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Pypes Off-Road X-pipe (99-04 GT)

100+ Reviews
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  • Item #20004
  • MPN# XFM16

  • Market Price $221.99
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Product Videos Customer Photos
  • Balance Out Exhaust Gases for More Power
  • Raspy Race Car Growl
  • Pypes Modular Construction
  • For Off-Road Track Use
  • 2.5" 409 Stainless Steel Tubing
  • Fits 1999-2004 GT Mustangs
Balances Exhaust Gases. Pypes Off Road X-Pipe is second to none when it comes to balancing out the gas pressures in your exhaust system. This Pypes off road x-pipe creates more power and torque than a traditional H-pipe. Why? Because the exiting exhaust pulses are merged at the "X", resulting in less exhaust back pressure for more power.

Race Car Growl. This free flowing Pypes x-pipe for the 1999 to 2004 GT's not only increases power, but it also adds a raspy, race car growl to the sound of your exhaust with its modern "X" crossover pipe design.

Modular Construction.   Pypes unique three piece modular construction makes it quick and easy to add or remove a catalytic converter to your exhaust system in just minutes depending on your driving needs.

Durable Stainless Steel Construction.   Pypes uses sturdy 16 gauge 409 stainless steel mandrel bent 2.5" tubing for improved flow and features welded reinforcement plates for additional strength.

Application. This Pypes Off-Road X-pipe is designed to be a direct bolt-on for the 1999 to 2004 4.6L V8 GT Mustangs with either aftermarket short tube headers or the factory manifolds installed. Intended for off-road, track use only, does not include catalytic converters.

Technical Note: 2004 model year Mustangs will require the use of 18" O2 sensor plug-in extender wires!

Fitment: 1999 2000 2001 2002 2003 2004 Details

What's in the Box
Hardware included:
  • (2) 2.5" clamps
Installation Info
Tech Specs
Mid Pipe Specifications
Style Mid Pipe: Standard length "X" Type Headers Required: Shorty
Piping Material: 409 Stainless Steel Piping Size: 2.5"
Catalytic Converter: "No" - For off-road use only Fitment: 1999-2004 GT Mustangs
Will it fit my Mustang?
  • GT - 99, 00, 01, 02, 03, 04

Fits GT Only

Most Helpful Reviews


Huge difference Highly Reccomended product! Great combo with Flowmaster 40\'s series mufflers

Helpful (1)

Best Set Up

Just installed this O/R x pipe On my 99 GT with a set up of SLP loudmouths an let me tell u its LOUD, its the best set up, i was trying to find that rite sound an this did the job, id recommend this product ...

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Helpful (1)

Overall Rating 4.1 out of 5 stars
Read All 100+ Reviews

Review & Install Video

Hey everyone, I’m Justin with and this is our power pack bolt on build up series, for all 99-04 Mustang GTs. With this power pack, we’ve put together some products that we feel are great first time mods, that would give any 99-04 GT a serious boost in power. So we’re going to get a quick baseline run, then hand our GT over to the crew so they can get started installing our power pack. Hey what’s going on Mike? Mike: Hey man, nothing, just finished the installation of our mods and we’re about to make another Dyno run. Justin: Very nice, yeah it looks good under here, what you got installed under the hood? Mike: Well first we installed Airaid cold air intake kit that comes with a high flow reusable air filter, so you never have to replace it. The Airaid’s going to increase air flow for the engine and allow it to breathe better and make more horsepower and it’s also going to help on fuel efficiency. Justin: Yeah, if you can stay off the pedal, right? Mike: Yeah. Justin: I see we’ve also got the BBK installed, what’s up with that? Mike: This is the one piece throttle intake, that features the throttle body and the plenum, that way you can have a bigger throttle body and not worry about restricting the air flow with a factory plenum. Justin: Mike, I know with this generation and these mods, we shouldn’t really need a tune right? Mike: Right, we don’t require a tune, but we are going to install a Bama performance custom tune, just to kind of tie everything together. Especially on our automatic, it’s going to help with our shift firmness, our shift points, and overall. Justin: That’s awesome, I know in conjunction with these mods we also have the Pypes off road X pipe going on, along with that Flowmaster American Thunder series Cat-Back as well, what kind of numbers are you expecting from all these mods? Mike: We should expect to see about 20-25 horsepower. Justin: Sounds good to me man, you ready to do another run? Mike: Absolutely, let’s do it. Justin: So our baseline run on our automatic 2000 GT gave us 222 horsepower and 260 ft/lbs of torque, with our powerpack installed, we made 249 horsepower, and 295 ft/lbs of torque, giving us a peak gain of 27 horsepower over our baseline numbers and gains of 35 horsepower and 54 ft/lbs of torque throughout the curve. So as you can see we’ve just finished off our second Dyno run and we’re definitely happy with the results, the best part is all these mods are installed easily in just a few hours using basic hand tools. Now let’s get our GT off the Dynojet and onto the streets, so we can hear that Flowmaster in action, and see what these mods did for our motor. Alright, now we’ve got our GT out of the shop and onto the streets and been able to put it through its paces a little bit, it’s easy to see why these bolt ons are such a popular first choice with so many Mustang owners out there, especially these 99-04’s. Those bolt ons really woke up our 2 valve motor, especially when paired with our Bama tune, which has really firmed up our shifts as well. So be sure to check out some of our other 99-04 bolt on build ups where we improve our handling, work on our acceleration, and dress up our GT a little bit.

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5 Questions / 7 Answers

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Do the pypes offroad x-pipes fit on my 01 bullitt?


Answer This Question I need this answered (0) (0)

Will my check engine light stay on if i use this X-pipe? If I was to use this pipe will It keep my check engine light on or will it stay off? And if it does stay on is there anything I can get to get it to go off?


  • Using this Off-Road X-pipe will cause your CEL to turn on due to removing your catalytic converters. You have two options to turn off the CEL, both of which I've attached below for you. You can purchase the MIL Eliminators, which sole purpose is to turn off the CEL caused by off-road mid-pipes. The other option is to get a custom tune for your Mustang. It will turn off the check engine light as well as improve the overall performance of this mid-pipe upgrade. It automatically enrolls you in our Free Tunes for Life Program so you can receive updated tunes when you do any future mods as well! Feel free to contact us with any further questions!


    Good Answer (3) (0)

Question Resolved

Will this fit on a mach 1?


  • Yes, had one on my 03 Mach 1, and it sounded great. Video clips below...


    Good Answer (1) (0)

Answer This Question I need this answered (0) (0)

HP? With a tune how much horse power will this add?


  • Probably between 15-20rwhp with a tune maybe more if u got headers


    Good Answer (0) (0)

Show 2 more answers Question Resolved

Before CatBack/O2 Sensors Is this before the cat back and do i need o2 sensors front or back i don't know which ones to get if i need them also will this pass ohio's e-check with pypes violators cat back and this offroad x pipe?


  • The Pypes Off-Road X-pipe (99-04 GT) will be after the cat-back exhaust going towards the front of the car. You will not need to replace your O2 sensors, but you will need MIL Eliminators to turn off the check engine light that will appear after installation. Since the laws and regulations are different across the country you will want to check with your local inspection station first.


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Question Resolved

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Customer Reviews (100+) Write a Review

Overall Rating 4.1

out of 5 stars

Installation Time:Afternoon

Installation Cost:$100-$250

  • Loudness / Volume 4.592593 4.6
  • Exhaust Note 4.703704 4.7
  • Fit & Finish 4.259259 4.3
  • Bang For Your Buck 4.555555 4.6

  • 5/5

    Installation Time: Less than 1 Hour

    September 25, 2012


    Me and a buddy had this intalled in just under an hour! Absolutely fit perfect. Started my car and it had that lovely growl that made me proud to own a mustang. Super aggressive sounding when you get on the gas. Great improvement for under $200. My only complaints with this are that it didn't come with new bolts for mounting up to the cat backs and it didn't come with any stickers for my tool box. Definately recommend this for any mustang owner!!


    Year: 2000 Submodel: GT Horsham, PA, USA

    Helpful (1) (0)

  • 1/5

    March 15, 2011

    dont buy

    Absolute garbage, nothing but leaks, dosent bolt up right, all the ball and flange connections leak, xpipe hangs sideways.

    kevin smith

    Year: 2000 Submodel: GT

    Helpful (1) (0)

  • 5/5

    December 07, 2009

    Best Set Up

    Just installed this O/R x pipe On my 99 GT with a set up of SLP loudmouths an let me tell u its LOUD, its the best set up, i was trying to find that rite sound an this did the job, id recommend this product to anyone, Thanks American Muscle

    Dustin Gomez

    Year: 1999 Submodel: GT

    Helpful (1) (0)

  • 3/5

    September 23, 2009


    the exhaust sounds great but is a comeplete pain to install. i had to cut mine and modify it to get it to line up. not a direct fit but it was worth the time. i rated it a 3 because of the difficulty when its supposed to be a bolt on replacement but performance and sound are everything its said to be


    Helpful (1) (0)

  • 3/5

    April 07, 2008


    The new 3 piece design helps with install. Some minor tweaking to make it fit right might need to be done.

    Dave B.

    Helpful (1) (0)

  • 5/5

    November 28, 2007


    Huge difference Highly Reccomended product! Great combo with Flowmaster 40\'s series mufflers


    Helpful (1) (0)

  • 3/5

    January 27, 2010

    Get what you pay for

    I want to start off by saying that is a very professional and customer satisfactory driven company. These are good quality pipes... for the price; however, there were too many complications with them. Starting with the down pipes: They bolted up fine to the stock exhaust manifolds (be sure to replace the gasket on the passenger side! Also, be sure to use the "sleeve" for the drivers side) but the pipes really should have come with washers for the down pipe-header connection. The "X" pipe: There was a definite flaw with the angle of its bends or weld placements. There was no possible way to line it up correctly to fit the down pipes, granted it was good quality welding. The ball flare connections are like something out of a horror film, they are way too "ball" shaped and not lined up to make a good seal with the Cat-back portion of the exhaust. The assembly of the mid-pipe: (Where the X portion of the pipe and the down pipes connect) The product comes with clamp bands, I do not know for sure if it was the quality of the clamps or the notches cut into the Pypes, but there is no possible way to make a correct seal with them. (I tighten the clamps until there was no more thread and the "x" would still slide right off of the down pipes). When I called Pypes customer service they told me that with this application "it's usually a hit or miss kind of thing" but they did offer me a "sorry". In the end, I lined up the exhaust with the down pipes bolted in and welded the "X" into position. The install took a couple of days (one whole day and night to figure out I wasn't just an idiot that couldn't read directions and another whole day to say, eff it and just weld it. My mechanic told me he would have given me a good deal and installed it for $90 including any cutting or welding required. I know there are people who got this and it fit right in, but when the actual manufacturer says "hit or miss... sorry" then I wouldn't take the chance. Also AM's policy on returning exhausts are "12. Returns will not be accepted for any of the following: Chips and Tuners, DiabloSport and SCT products, Wheel/Tire Packages, Opened Clutches (removed from original packaging), Opened Exhaust products (removed from original packaging)..." You must open the box first to be able to tell that the pipes do not fit correctly, so the instant you do open it you are stuck with the product. AmericanMuscle offers a large selection of "X" and "H" pipes of much higher quality. I highly recommend purchasing another brand for a little bit more money (it's money you would be having to spend regardless). After the fact, it sounds good. The "X" is very raspy (which is THE biggest difference between it and the "H") and definitely wakes the neighbors. Be sure to purchase the MIL eliminators, they are a great price and work amazingly (plug them into the rear O2 sensors, you only need one pair even though someone here thinks otherwise). I'm taking the time to provide as much information as possible with my experience because I wish someone would have done the same, now you can't say I didn't warn you. In my honest opinion, the Pypes are an alright price for an alright product.


    Helpful (41) (0)

  • 3/5

    June 04, 2010

    great sound, horrible fit

    if you dont have a swivel socket or a lift it is extremely hard to put these on. had to bring mine to a shop to get them to fit right. and i still have leaks where the pipes fit together. i gave it 3 stars for the sound, 0 stars for fitment and quality. not gonna stop me from ordering fro AM though. :D


    Helpful (3) (1)

  • 1/5

    January 30, 2010


    I also must say that AmericanMuscle is very good with there customer service, how ever pypes is not ! Lets start off by saying im no stranger to working on cars, that being said this is what my problem is. I order the pypes XFM16 off road x pipe with the intention of improving the sound and power of my car, i read the reviews on the product and a while back there were a few other complaints that this X pipe dose not work, and then all the sudden there are quite a few that say they do. Well i decide it seems like pypes has fixed the problem, so i buy it. When i recieve the package, the first thing I do is open it and get all excited on how great my car is going to sound with its new exhaust system. I then start to notice the ball flange that conects to the catback exhaust and i realize its going to be almost impossible for a good seal, but out of bad judgment i decide to go ahead and use them. I read the instuctions very carefuly and begin the install. To start off everything is going good except there appears to be a small gap between the manifold and the drivers side down pipe. Well i bolt it up anyway and torque everything down i notice that the x pipe that connects to the down pipe seems to be at a slight angle so i tug on it and sure enough it slides out of the x pipe so i take it all back apart and re install the x pipe. So after I put it all back togather i still have the same problem but i go ahead and start the stang. With the car running i notice a awful exhaust leak so i turn the car off and right away call pypes to ask if there were any other procideurs i should have taken while instaling the x pipe. To start off pypes was very polite in helping and told me to take it off and check for alignment again, so this time I decide to take the car to the school and put it up on a car lift to do the install, only to have the same problem but then i notice the reason im having the offset and the leak is because the stud that goes inside of the manifold has a spacer that ford has put on there. So i call pypes once again to only find out that they are closed, this time I call American Muscle and talked to there staff, they finaly get pypes on the phone and talk to the guy that designed the x pipe and they give me his name and tell me to call. As so as i get off the phone with AM I call pypes with the guy that designed it expecting my call but guess what they dont answere talk about customer support! Well that was on a firday so i knew that they were going to be closed for the weekend so i take the pipe off, and install the stock H pipe back on. And drive home, first thing monday morning I am on the phone with pypes, and get a new person this time. He tells me that in 2003 half of the ford mustangs had the studs that had the spacer and the other half did not and that i was going to have to replace the studs. Well im a little upset at this point and say ive spent this much money on the exhaut whats one more thing, then only to find out Napa, Slacks, Auto Zone, and Advance Auto do not carry this particular stud. At this point i call and talk to pypes and they tell me there is no way to get the money back for the exhaust since its been ran, well I think that is about the stupidst thing I have ever heard in my life because how in the heck are you suppose to check for an exhaust leak with out starting the car? I hope this review is helpful for somone wanting and x pipe I can guarante you that you dont want this one and that I will never again purchase a pypes product. There are differnt x pipes out there that are a little more expensive, but im sure they have got to be better quality than this.


    Year: 2003

    Helpful (21) (2)

  • 1/5

    February 12, 2011

    Buyer Beware

    Sorry Pypes, maybe next time. To the consumer: If you buy this off road x-pipe, you will be wasting your money. I too was drawn in by the outstanding price on a stainless mid pipe. I'm a maintenance fabricator/millwright by trade. I can install and/or fix anything. Well, so I thought. Quality seemed great. Installation right out of box, near impossible. Nothing lines up. Since installing a year ago, my baby has been in the air over 4 times battling leaks. Then to an exhaust shop twice trying to get the leaks stopped. HUNDREDS after purchase spent. After having to cut mid pipe in 5 places, re-bend tubing (trying to obtain a moderate alignment), completely welding cuts and seams, I thought I finally had it. No leaks and sounded great. Looked like Frankenstein. Thinking my troubles were over, the exhaust tubing is now starting to stress crack right next to welds and is creating all new leaks. I'm freaking done!!! $200 for exhaust? $100 on first trip to exhaust shop? $120 on second trip to exhaust shop? Countless hours spent under car, bloody knuckles, and cursing till the cows come home? After all that, I'm still left with an exhaust mid pipe that is leaking horribly. And now I get to go spend another $300-$400 on a new, higher quality mid pipe. What a joke... If you are looking for a stainless mid pipe, save money by spending a little more. Buy a different manufactures mid pipe. Sorry to say, but Pypes failed on this one. AM, your still the best. Keep up the great work.

    Errol S.

    Helpful (10) (0)

  • 2/5

    February 17, 2011

    Okay for the money but...

    I bought these pipes in hopes of saving some money but I should have gone with a better set. They do not come with any studs or gaskets to replace the factory set. Fairly simple to install but the down pipes do not match up with the "x" and there is a large gap on the passenger side. I have never been a big fan of clamps and this is no exception. Nothing but leaks! The old gasket on the header leaks. The clamps leak. The cat-back connection leaks and when I run at about 2,500 rpm, the pipes resemble the sound it makes when you hit a chain link fence with a stick! Not at all the sound I was looking for... I'm about to drop a few extra bucks and buy a one-piece x-pipe so I don't have the same problem as I had with these.

    Lance Harrison

    Helpful (10) (2)

  • 5/5

    December 28, 2009


    put these on with the JBA headers and slp LM2 sounds amazing everything fit properly, and its all made with great quality i recomend this product to anyone who wants to make there stang louder thanks AM


    Helpful (4) (1)

  • 5/5

    December 03, 2009

    Very Unique

    I've recently installed a 3 piece Pypes's O/R x pipe on my 2000 GT. Let me tell you, I love the sound; that combined with Magnaflow weld-ins is music! It's got a rasp and a nice rumble at low rpm but as the revs get higher it really opens up. As it climbs to 3500-4000 rpm it starts to scream. Very low drone on the highway, nearly silent in 5th at 65 mph. Everything about the sound is great, however look out for the fitment. I've heard that these can be hit or miss on the fit so taking it to a shop is recommended.


    Year: 2000 Submodel: GT

    Helpful (8) (4)

  • 5/5

    June 18, 2009


    This x-pipe sounds amazing!! Combining it with flowmasters produces the best sound you will ever hear. My friends can hear me coming from down the street and all i get is compliments. This was a great buy and i will definitely be buying from American Muscle in the future.


    Helpful (7) (4)

  • 4/5

    Installation Time: Shop Install

    October 24, 2011


    I bought this for my 2003 Mach 1 not knowing very much about Mustang exhaust. This was the only mod I did to the exhaust, only because after hearing it I didn't want to change a thing. It was very loud classic hot rod sound. I couldn't be more pleased with the sound. Only draw back was possibly due to Pypes craftsmanship. I noticed after awhile a small leak from a crack around a weld to the O2 sensor mount. Other than that I have nothing bad to say. Great product and great price.


    Year: 2012 Submodel: GT Lovington NM USA

    Helpful (3) (1)

  • 5/5

    July 15, 2011

    pypes o/r x pipe

    First off I wana say that you should ignore 3/4 of all the reviews on this product saying that it doesn't work. Now with that being said this is not a pipe that you should try installing yourself. Take it to your local exhaust professional and let them do it. All of these reviews talk about how the product does not fit up right or that it leaks like crazy. If it is not fitted up just right then this will be the outcome, but I had a local exhaust shop install mine and it worked out great. The sound is awesome and Ive checked it 3 times for leaks and cant seem to find one. It is honestly a good product its just the installers fault on most of these reviews. Don't be afraid of this product, it has a very aggressive throaty tone with a mean rasp to it.

    Justin W.

    Year: 2003 Submodel: GT

    Helpful (4) (2)

  • 4/5

    October 16, 2009

    Pypes Offroad X-pipe

    THis product is awesome. It is cheaper than most x-pipes, but it still gives just as much horse power with a more aggressive sound on my 03 GT. It is more free flowing than the old H-pipe so I kept my MAC catback system on and the compression to the rear is perfect. The only problem was the fit. It was an 2 inches off on the passenger side connecting to the catback, luckily I was already at a muffler shop shop. Rpm's are a little quicker and my gas mileage is better. I dont know about all Gts, but my engine light stays off. Got lucky on that one, Thanks AM!


    Year: 2003 Submodel: GT

    Helpful (4) (2)

  • 4/5

    Installation Time: Full Day

    May 14, 2013

    Be careful with the install..

    After recieving this X pipe, i was too stoked to wait another day to install. This was a huge mistake. 7 hours under the car, sore shoulders and elbows lead to nothing but exhaust leaks. Before commiting to the install of this pipe, make sure you have the following: 4 3/8's" hex bolts 8 3/58's washers 4 matching 3/8's nuts (The above is for the cat-back connection portion) Ultra copper RTV O2 Sensor ratchet socket First of all, on your O2 sensor removal, Pypes recommends using a 22mm open end. AVOID THIS. It will round off your O2 sensor bolts if you're a higher mileage mustang like mine. Buy the socket, it's worth it. Once you have that off, purchase another passenger side gasket. RTV the snot out of it as well as the collector connection. Also, RTV the snot out of the bell flange for the driver's side. MAKE SURE IT'S SENSOR SAFE RTV. This pipe isn't top quality.. you'll need gasket to avoid leaks. Once you have those two header connections on, quickly attach the X portion. this might require you to drop your driver's side axle-back to get it to slide into place. Re-install, and crank the U-clamps to the best of your ability. You'll still leak around the clamps, something some RTV or putty won't fix. The fit and finish is the biggest problem with this pipe. Too much is required to get it to stop leaking. Once it stops leaking (3 trips under the car later) it sounds great. Awesome sound. I only hope it holds up!!


    Year: 2004 Submodel: Mach 1

    Helpful (1) (0)

  • 4/5

    Installation Time: Afternoon

    July 08, 2012

    with patience comes success

    I picked this x pipe up for my 03 gt. Honestly I had more trouble removing the passengerside outside nut from the stud off the manifold than i did installing the x pipe. The install should really take less than a hour as long as you can remove the old mid pipe in a timely manner. you really have to adjust the ban clamps in my case several times. mine leaked from the slits in the slip joints from the X to the down pipes until i finally got them right. not a bad x pipe it sounds SICK bolted to a bassani cat back i will order one again for sure for our 01 cobra , its no bbk but it does the job . AM keep up the great work. !! ps be sure to order you mil eliminators as well unless you want to see you cel!!!


    Year: 2003 Submodel: GT maryland

    Helpful (1) (0)

  • 5/5

    Installation Time: Afternoon

    May 05, 2012

    Fits great sounds mean

    The hardest part about insthalling this xpipe was taking the old hpipe off other than that it fits grat and once you get the old pipe off takes about an hour to insthall. My 04 Mustang GT has shown noticeable gains in hp and tourque since the instillation and has a very deep mean growl to it. This is a great purchas


    Year: 2004 Submodel: GT Lebanon, OH, USA

    Helpful (1) (0)

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