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MAC Off-Road Pro Chamber Mid Pipe (99-04 4.6L)

AmericanMuscle no longer carries the MAC Off-Road Pro Chamber Mid Pipe (99-04 4.6L). Please check out 1999-2004 Mustang H-Pipes for an updated selection.

Features & Details

  • Improves Exhaust Flow for More Power
  • Unique Pro Chamber Crossover Design
  • For Off-Road, Track Use
  • 2.5" Mandrel-Bent Aluminized Steel Tubing
  • Fits 99-04 GT, Bullitt, Mach 1 & SVT Cobras
Increase Exhaust Flow. Get rid of those power robbing factory catalytic converters and uncork your Mustangs hidden power with a MAC Performance Off-road Mid-Pipe. Featuring their exclusive Pro Chamber style crossover and free-flowing mandrel-bent piping, this high performance Mid Pipe will dramatically improve exhaust flow for more horsepower and torque.

Aggressive Muscle Car Rumble. This free flowing MAC off-road Mid Pipe not only increases the horsepower and torque of your Mustang, but with its unique Pro Chamber cross over design it adds a more aggressive muscle car rumble to the sound of your exhaust, that the standard H-Pipe just can't match.

High Quality Construction. Mandrel bent from durable 2.5" steel tubing so there are no kinks to rob you of power, this MAC Performance Mid Pipe has been hot-dip coated with aluminum-silicon alloy to aluminize the steel to protect against corrosion and rust.

Application. This MAC Performance Pro Chamber Off-road Mid-pipe is designed as a direct bolt-on for the 1999-2004 4.6L Mustangs, including the GT, Bullitt, Mach 1 and SVT Cobra Models with either aftermarket short tube headers or the factory manifolds and a dual catback exhaust installed. Intended for off-road, track use only, does not include catalytic converters.

Technical note: 2004 Mustangs require the use of 24" O2 sensor plug-in extender wires. This MAC Performance product is intended for off road use, and is not legal for use in emission restrictive states.

Fitment: 1999 2000 2001 2002 2003 2004 Details

MPN# PC9900

CA Residents: WARNING: Cancer and Reproductive Harm - www.P65Warnings.ca.gov

What's in the Box
  • (1) Mid-pipe
  • (2) Down Pipes
  • (8) Threaded Studs
  • (8) Nuts
Installation Info
Tech Specs
Mid Pipe Specifications
Style Mid Pipe: Standard length Type Headers Required: Shorty or Stock Manifolds
Piping Material: Aluminized Steel Piping Size: 2.5"
Catalytic Converter: "No" - For off-road use only Fitment: 1999-2004 GT, Bullitt, Mach 1 and Cobra Mustangs
Will it fit my Mustang?

    Customer Photos (14) Submit Your Photo

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      Questions & Answers (12)

      5 Top Rated Questions

      Pairing up with hig flow cats i have flowmasters welded into my stock mid pipe, and the sound is nice, but i need a little bit more umph. Unfortunately in MA, I need to have cats to pass inspection. Would i be able to have hig flow cats welded into this mid pipe, and will it still give me that extra umph for exhaust tone and loudness with the high flow cats in? Thanks in advanced guys. And no, i do not want to switch mid pipes every year just for inspection!

      • jay281GT, Depending on the length of the aftermarket cats you choose, they should fit!, the sound change will be minimal with high flow, but a little quieter in my opinion. Any reliable exhaust shop should be able to make the necessary changes for you, if you do not have any local to you, We do have a few catted mid-pipe options for you! Hope this helps, Forrest

      Helpful (1) Show 2 more answers

      I was wondering will i need o2 sensor extensions and mil eliminators to install this any help would be appreciated

      • It depends on the year of your Mustang. If you have an 03-04 Mustang GT you will need the extensions. If you have a previous year then you don't. My 2001 GT sat perfectly, stretched but just the right amount.

      Helpful (1) Show 2 more answers

      Hello, Can this Pro Chamber mid pipe be hooked up to the MAC long tube headers? and if not, does MAC make a set for such headers? or can you recommend other options? Thank you!

      • This Pro Chamber mid-pipe will not be compatible with long tube headers due to them being designed to work with the factory exhaust manifold or shorty headers. We do carry these here that would work with the MAC long tube headers: https://www.americanmuscle.com/mac-shorty-prochamber-9904gt.html& https://www.americanmuscle.com/mac-offroad-pro-chamber-mid-pipe-9904-gt-cobra-w-long-tube-headers.html. 

      Helpful (0)

      Is this interchangeable with Mac o/r x pipe?

      • The MAC Off-Road Pro Chamber Mid Pipe and X-Pipe are interchangeable.

      Helpful (0)

      Will this mid pipe work with mid length headers or does it only work with short headers?

      • Mid-length/tuned-length headers have the collectors in the same position so they should both work with this MAC Off-road Pro Chamber Mid Pipe. Just be careful as manufacturing tolerances from brand-to-brand will change.

      Helpful (0)
      Post Your Question
      7 More Questions
      would I need o2 sensor extension on my 2004 mustang cobra? 1 answer
      After installing this midpipe. My exhaust is only about 2 inches off the ground. What can i do to make it sit closer to under the car. 1 answer
      I'm seeing the piping on this mid pipe is 2.5". Will it fit flush and not cause any exhaust leak combined with the Mac 3" catback exhaust? 1 answer
      I see a circular type adapter in the picture of the various hardware components. What is this and where exactly does it go? Any other need to knows or tips for install? 1 answer
      Im running a slp lm1 cat back im worried if this mid pype is going to make it quiter cause im trying to go for something to make it louder but also not too raspy but still sound good and turn heads. 1 answer
      do i have to remove old studs? will i have to remove the old studs in my stock manifold to install this pipe? I read somewhere that this pipe won't tighten down all of the way because the studs on the stock manifold are too long. any truth to this? it would help if there was an installation guide 1 answer
      Check Engine Light? Will installing this midpipe turn on the check engine light? 2 answers

        Customer Reviews (62) Write a Review

        Overall Rating 4.6

        out of 5 stars

        Installation Time:Afternoon

        Installation Cost:$100-$250

        • Loudness / Volume 4.431035 4.4
        • Exhaust Note 4.793103 4.8
        • Fit & Finish 4.327586 4.3
        • Bang For Your Buck 4.431035 4.4



        • 2/5

          Installation Time: Shop Install

          Installation Cost: $500-$1000

          September 28, 2018

          Poor fitment

          Well I ordered the bbk shorty headers along with the pro chamber and the mac catback exhaist to put on my 01 gt. Right now it's at the shop and the people at the shop are chopping up the pro chamber because it is to long and the catback will not fit. The headers are a problem too. Bbk sent bolts that were to long and had to be cut down. The installation was going to cost $300 but as of right now I'm looking at $650 if nothing else goes wrong.

          CodyS

          Year: 2001 Submodel: GT

          Helpful (3)

        • 5/5

          June 21, 2018

          Great sound

          I bought the pro chamber and tge Mac boom tube exhaust for my 2000 Mustang GT. These 2 paired together sound amazing!

          DannyB

          Year: 2000 Submodel: GT

          Helpful (5)

        • 5/5

          Installation Time: Less than 1 Hour

          May 07, 2018

          2003 Saleen S281 Mustang

          I did a lot of research and review before pulling the trigger on an off-road mid-pipe and the money you pay for the MAC Prochamber is worth every penny! I wanted the power of being catless, but not being obnoxiously loud either like some of these X/H pipe setups. I daily drive my Saleen when the weather is right, so I didn't want to have any drone or always being worried about getting pulled over for the loudness. Well the MAC Prochamber paired with Pypes M80 mufflers and 4" tips was exactly what I was looking for! The sound is great, it is a lot louder than my previous Catted X pipe setup but mostly, it's enjoyable and you can hear the car coming from blocks away. The torque/power you gain is also one of the best of the mid-pipes for these stangs. Definitely gives you that "throw you back in the seat" feeling. I may upgrade my mufflers to LM1's/ Stingers/ATAKS just to give it more growl, but either way I love this mid-pipe much more than any of the X/H pipes on the market!

          Pollock

          Year: 2003 Submodel: GT

          Helpful (7)

        • 4/5

          Installation Time: Afternoon

          May 01, 2018

          perfect

          I paired this with pypes m80 mufflers/catback and it sounds great. very nice rumble without the raspy sound.

          IsaacC

          Year: 2001 Submodel: Cobra

          Helpful (7)

        • 5/5

          Installation Time: Less than 1 Hour

          December 10, 2017

          Great sound

          I replaced a bbk offroad x pipe with this i liked the bbk at times and it was LOUD but a little to raspy for me and would get crazy loud at like 2000 rpm even when driving slow and i always got dirty looks from people thinking i was driving fast when i wasn't i put in the prochamber and there is no more rasp and it has a much more old school sound too it very quiet inside the car which is nice and is fairly loud outside without being obnoxious and i feel like i gained some low end torque which i lost with the x pipe only complaint is I had to retap a few of the threads but overall very happy

          MartinH

          Year: 2003 Submodel: Mach 1

          Helpful (8)

        • 4/5

          Installation Time: Afternoon

          December 02, 2017

          Satisfied!

          I would have given this a 5, but for a few issues. I have a 2003 Mach1. The minor issues with my vehicle were as follows: the hardware was missing 2 nuts. There are four sets of bolts to attach. Three have threaded flanges, the third requires nuts which were not supplied. I had to stop the installation to run to the hardware store. The next issue is that the placement of doggles for the O2 sensors were offf, luckily there was enough play in the harness, (drivers side front), to allow me to attach the sensor. Passenger side rear O2 could not be mounted in the stick bracket and I had to zip tie it out of the way. Just an FYI if your working with the 4.6 cobra motor be prepared for those issues. On the upside once the obstacles were overcome the performance was as advertised, car is much more aggressive and it sounds sweet. No regrets! 2 hour install

          FrankB

          Year: 2003 Submodel: Mach 1

          Helpful (8)

        • 5/5

          Installation Time: Less than 1 Hour

          November 21, 2017

          Like a glove!!!

          I had the MAC O/R X-pipe with the Magna-Pack Cat-backs, and it was loud, too loud for the cops. It had that snap from the x-pipe and it attracted alot of attention. I got the Pro-chamber and only had to swap out the crossover center section, and its still loud, but instead of that snap it has it's rumble back. Only took a half an hour. Very happy with the whole package, pricey, but worth it.

          JohnnyKipp

          Year: 2003 Submodel: Mach 1

          Helpful (9)

        • 3/5

          Installation Time: Afternoon

          September 04, 2017

          the noise its great buuut...

          the sound is 100 better and the exhaust note is just right but the fitment is questionable, the flange that connects to the manifold on the driver side is way too big that no matter how much you tighten it, it won't seal and it's quite loose. Just keep in mind that welding might be in order for better fitment. Also, either storage or handling could be better the connection tips bend really easy. Finally, for what it is, it's a little pricy and the craftsmanship is wanting. If you are looking for noise go for the x pipe its cheaper, equal performance and noise

          AlexOchoa

          Year: 2001 Submodel: GT

          Helpful (9)

        • 5/5

          Installation Time: Afternoon

          July 19, 2017

          Please read!!

          I replaced my factory cat back with Borla Ataks. I wanted to be a little bit louder so i went ahead and purchased the BBK off road X-pipe, worst mistake i ever made. So i purchased the Mac Prochamber. This on the other hand has easily been one of the best upgrades i have made to my car! I got the loudness i wanted and get thumbs up for it. The BBK x-pipe all i got were dirty looks and people hating it. Overall i recommend this Prochamber to anyone!!

          DanielT

          Year: 2004 Submodel: GT

          Helpful (7)

        • 5/5

          Installation Time: Afternoon

          July 17, 2017

          Loud!!!!!!!!!

          This is exactly what my 04 cobra needed. I originally put the slp loudmouth 1 catback on it and it wasn't enough. So I did my research and bought the Mac prochamber and wow what a difference my car sounds awesome and gets plenty of compliments.

          EverettC

          Year: 2004 Submodel: Cobra

          Helpful (7)

        • 2/5

          Installation Time: Afternoon

          May 24, 2017

          Disappointing

          While previous products from MAC have been exceptional, this kit was all wrong. Does not fit the studs in stock exhaust headers. Incorrect gasket, should come with a metal flanged gasket. Down pipe to hbox bent wrong and is too short had to pull exhaust off of hangars to fit. Threaded holes in flanges and bolts provided are incorrectly sized had to rethread. Still fighting exhaust leaks and waiting for parts. Hoping to have everything together by the end of the week

          JamesR

          Year: 2004 Submodel: GT

          Helpful (8)

        • 5/5

          Installation Time: Less than 1 Hour

          February 16, 2017

          Best H pipe

          I had a bbk X pipe with SLP 1s way to loud and raspey didnt like it at all. Changed it out with the pro chamber now it sounds sick. Its loud when i hit it hard but with a deep tone no rasp at all and with my bama tune no check engine light and lets not forget that nice smell of cattless exhaust when at a red light install took an hour and costed 120.00 at local shop in NYC I could not be happier got my pro chamber in 2 days fast shipping highly recommended

          Beast

          Year: 2000 Submodel: GT

          Helpful (8)

        • 5/5

          Installation Time: Afternoon

          December 03, 2016

          Perfect!

          I just purchased this mid pipe and absolutely love it! Tons and tons of smiles when I first started it up. I highly recommend this product to anyone who is wanting that old school classic muscle car sound. Nice tone and quality with zero raspy notes. The toughest part is just removing the factory exhaust bolts. Once you're finished removing the factory H-pipe, it installs super easy.

          Iggy

          Year: 2000 Submodel: GT

          Helpful (7)

        • 5/5

          Installation Time: Less than 1 Hour

          November 20, 2016

          Mac ProChmaber

          I received the mac prochamber within a week of ordering it and I love in Cali so thanks AM. Package was in great condition and it was a flawless delivery. My back was out so I had the shop install it for me. Easy install they said. Had them attached the MIL Eliminators as well so no CEL for me. The sound difference is dramatic. Not really any noticeable drone. Louder cold start and thumpy idle. Anything past 2000 RPMs and it screams, similar to an X pipe. Nice low and mid range power increase. I do have this paired up with the SLP LM1 catback as well. I do feel vibrations against the subframe but I believe that to be an install issue not a product one at all and one I'm sure it will be easy to fix. Overall it's a great product. Thanks AM!

          MachMike

          Year: 2003 Submodel: Mach 1

          Helpful (9)

        • 5/5

          August 26, 2016

          That sounds awesome

          Nothing like a MAC Prochamber with a Flowmaster Catback. My favorite Mustang sound!!!

          PoppaG

          Year: 2002 Submodel: GT

          Helpful (10)

        • 5/5

          Installation Time: Less than 1 Hour

          June 28, 2016

          Couldn't be more impressed!

          Purchased this product because it was on sale... I've been keeping my eye on it for a while and when it went on sale I scooped it up. Had it installed where I work and after the first startup nothing but looks from all the technicians in the shop lol. Not to mention the smile on my face. Deep aggressive exhaust tone. Little raspy above 4500 rpm but nothing a couple resonators can't fix. I'm sure it's raspy because it straight piped from behind the Hpipe. But overall great purchase and only took 3 days to get to my house. Once again AM never disappoints.

          SilverGT

          Year: 2000 Submodel: GT

          Helpful (7)

        • 5/5

          Installation Time: Shop Install

          Installation Cost: $100-$250

          June 22, 2016

          Best of both worlds!!!!

          Between an X pipe and H pipe This midpipe is definitely the best of Both!!! Deep hollow sound! Reccomend to everyone!

          Lorenzo

          Year: 2002 Submodel: GT

          Helpful (7)

        • 5/5

          Installation Time: Afternoon

          June 20, 2016

          Amazing Sound!

          I absolutely love this mid-pipe. I have flowmaster original 40 series mufflers and with the Prochamber combination, it creates an aggressive and deep sound. It is music to your ears. Also the fit is perfect but the finish could be better. Other than that small flaw, I would definitely recommend this product to anybody. .

          Nikandreos

          Year: 1999 Submodel: GT

          Helpful (7)

        • 5/5

          Installation Time: Afternoon

          June 13, 2016

          Can you say V8?

          I have a 2001 cobra with flowmaster super 44 weld ins .. i installed the mac prochamber yesterday and i got exactly what i was looking for ! Sounds really deep with NO raspy-ness at all , it sounds like a true muscle car ! Plus i can really feel the power gains .. i used to chirp second with 295's now when i bang second she gets sideways ! Overall great mod for the money!

          casey

          Year: 2001 Submodel: Cobra

          Helpful (7)

        • 4/5

          June 10, 2016

          Sounds great

          Pro chamber is sick sounds great not too loud just the right tone

          JonnyO

          Year: 2002 Submodel: GT

          Helpful (7)

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