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

Item 40000
AmericanMuscle no longer carries the MAC Off-Road Pro Chamber Mid Pipe (99-04 4.6L). Please check out Ford Mustang Mid-Pipe Exhaust for an updated selection.
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    Product Information

    Features, Description, Reviews, Q&A, Specs & Installation


    • 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: Details

    CA Residents: WARNING: Cancer and Reproductive Harm -


    Customer Reviews (62)

    Write a Review

    Ratings Summary

    4.6 out of 5 overall rating from 62 customers

    Installation Time: Afternoon

    Installation Cost: $100-$250

    • September 28, 2018

      2 2001 GT - CodyS Installation Time: Shop Install Installation Cost: $500-$1000

      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.

      Helpful (3)
    • June 21, 2018

      5 2000 GT - DannyB

      Great sound

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

      Helpful (5)
    • May 07, 2018

      5 2003 GT - Pollock Installation Time: Less than 1 Hour

      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!

      Helpful (7)
    • May 01, 2018

      4 2001 Cobra - IsaacC Installation Time: Afternoon


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

      Helpful (7)
    • December 10, 2017

      5 2003 Mach 1 - MartinH Installation Time: Less than 1 Hour

      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

      Helpful (8)
    • December 02, 2017

      4 2003 Mach 1 - FrankB Installation Time: Afternoon


      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

      Helpful (8)
    • November 21, 2017

      5 2003 Mach 1 - JohnnyKipp Installation Time: Less than 1 Hour

      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.

      Helpful (9)
    • September 04, 2017

      3 2001 GT - AlexOchoa Installation Time: Afternoon

      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

      Helpful (9)
    • July 19, 2017

      5 2004 GT - DanielT Installation Time: Afternoon

      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!!

      Helpful (7)
    • July 17, 2017

      5 2004 Cobra - EverettC Installation Time: Afternoon


      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.

      Helpful (7)

    Questions & Answers (12 answers)

    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: 

    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

    Installation & What's in the Box

    Installation Info

    What's in the Box

    • (1) Mid-pipe
    • (2) Down Pipes
    • (8) Threaded Studs
    • (8) Nuts

    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

    • Bullitt - 01
    • Cobra - 99, 01, 03, 04
    • GT - 99, 00, 01, 02, 03, 04
    • Mach 1 - 03, 04