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Pypes Catted H-Box Mid Pipe (99-04 GT)

Market Price $702.99 You Save 12% ($82.31)
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  • Item 387279
  • MPN# HFM37

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Ship to: Ashburn - 20149
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    Features & Details

    • Increases Power
    • Deeper, Muscle Car Rumble
    • H-Box Center Chamber Design
    • Full Tig-Welded and Mandrel-Bent
    • 2.5" 409 Stainless Steel Tubing
    • High Flow Ceramic Catalytic Converters
    • 49 State Street Legal
    • Fits 1999-2004 GT Mustangs
    More Power. Add more horsepower and torque to your 1999-2004 GT Mustang by replacing those power robbing factory catalytic converters with a brand new Pypes Catted H-Box. The Pypes Catted H-Box is designed to offer increased horsepower and torque, as well as an even deeper sound dimension, when compared to your traditional H-pipe upgrade.

    Deeper Rumble. This free flowing Pypes H-Box for the 4.6L New Edge GT will not only increase power as a result of its perforated H design within the center chamber and the included ceramic catalytic converters, but it will also add a deep muscle car rumble to the sound of your exhaust.

    Durable, Stainless Steel Construction. Pypes utilizes high quality 16 gauge 409 stainless steel mandrel bent 2.5" tubing for increased exhaust flow and features fully Tig-welded reinforcement plates for additional strength. The included High Flow Ceramic Catalytic Converters far outperform the restrictive stock cats to provide a significant increase in horsepower and torque.

    Application. This Pypes Catted H-Box Mid-Pipe is designed as a direct installation for the 1999-2004 4.6L GT Mustangs, with either aftermarket short tube headers or the stock manifolds and a dual catback exhaust installed. Some cutting required for installation.

    Note. This H-Box Mid-Pipe is 49 State Legal - not Legal in CA - and is not CARB Certified. Please check your local and state ordinances for installation and usage regulations.

    Technical Note: 2004 Mustangs require the use of 24" O2 sensor plug-in extender wires.

    Fitment: 1999 2000 2001 2002 2003 2004 Details

    CA Residents: WARNING: Cancer and Reproductive Harm -

    What's in the Box
    • (1) H-Box
    • (2) Down Pipes
    • (1) Down Pipe Sleeve
    • (2) Catalytic Converters
    • (4) Clamps
    Installation Info
    Tech Specs
    Mid Pipe Specifications
    Style Mid Pipe: Standard Length H-Box Type Headers Required: Shorty Headers or Stock Manifolds
    Piping Material: 409 Stainless Steel Piping Size: 2.5"
    Catalytic Converter: Yes - Ceramic Fitment: 1999-2004 GT Mustangs
    Will it fit my Mustang?

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    Questions & Answers (5)

    5 Top Rated Questions

    I have a 2004 V6 and was looking to convert from the single exhaust to a true dual setup. This mid pipe says its only for the 99-04 GT but would it perchance fit with my stock V6 headers?

    Is this mid pipe fit with full length header pasestter ?

    • This would not work with long tube headers no.

    Helpful (0)

    Two questions really, does this [significantly] reduce interior drone and does this cause a power loss compared to traditional H-pipe?

    • It can help in the reduction of drone but it is not designed specifically to do so. With that being said your definition and my definition of significant drone reduction very well may be different. As far as power goes, every Mustang reacts differently, and the addition of an exhaust piece, other than headers, may have you gain power, lose power, or not change at all. It is also worth noting that the change in power, if there will be any, most likely won't be significant enough to notice a difference.

    Helpful (0)

    Will this fit an 04 Cobra?

    • Unfortunately, this mid pipe is only designed for the 99-04 GT Mustangs. It may not a direct bolt on to your 04 Cobra.

    Helpful (0)

    I was wondering if this product is compatible with the Mac catback (Item 40047) exhaust system, and stock manifolds on a 1999 Mustang GT as a direct bolt on system.

    • The Pypes Catted H-Box Mid Pipe (99-04 GT) is compatible with both the MAC Cat-Back Exhaust (96-04 GT, Mach 1) (Item #40047) and the stock manifolds.

    Helpful (0)
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    Customer Reviews (2) Write a Review

    Overall Rating 4.5

    out of 5 stars

    Installation Time:Weekend

    Installation Cost:$100-$250

    • Loudness / Volume 3 3
    • Exhaust Note 4.5 4.5
    • Fit & Finish 4 4
    • Bang For Your Buck 3.5 3.5

    • 5/5

      Installation Time: Shop Install

      Installation Cost: $100-$250

      October 31, 2017

      Pypes H Box Mid pipe

      For some reason they are actually slightly quieter than the stock H-Pipe that I replaced, but maybe they just aren't broken in yet. I really do like the deep rumble though, and they have cut down on the drone inside the car, AND, the car does seem a bit quicker, so in all I'd highly recommend. Only slight compliant- they hang low and seem to rub on everything, so I may have to re-install the original springs (I had it lowered about an inch and a half- but the stock H pipe didn't rub like this).


      Year: 1999 Submodel: GT

      Helpful (9)

    • 4/5

      Installation Time: Afternoon

      May 23, 2016

      First review for catted h-box

      Let me start by saying that I've ran three different mid-pipes now, the first, BBK off-road x pipe which was poor quality, trashed it, then went with Bassani, which is a freaking awesome company that produces great products with great finishes, and I loved it except when I would be at a stop with my windows down. Got really tired of smelling like gas haha. Anyway decided after I put my stock h pipe on that I liked the deep rumble instead of the raspiness of the x pipes. Ski decided to jump and be the first one to review this product. I looked everywhere for reviews, videos, anything, but there is literally nothing. Well for all of you who need to hear a review here it is. Shipping got it to me in a week, the package itself was very nice, and everything inside was wrapped and protected by styrofoam pieces. They include all the hardware. The welds themselves looked pretty good, not to choppy, and surprisingly the h box itself was really light. I would say maybe only 5-10 pounds. Everything looked like it would be a breeze to put in. So when I purchased this product I thought that they would have cut the downtubes from the factory for the cats to fit and all, well they didn't, and it's 409 steel so it's tough to cut. Just a heads up for the diy'ers like myself. After that though, same issues with any mid pipe install, got fhose ironed out and no leaks. Looks excellent underneath, the cats are super shiny chrome. My stang is lowered 2" and I have to say that after using a Jack on the h box and tightening it up it still hangs low, so be aware of that. I scrape all the time. now to the actual sound, I have the American thunder cat back with this setup, and I must say that at idle it sounds a little bit like its cammed. Just a tiny bit though. Daily driving literally sounds the same to the stock h pipe. Maybe like 2-5 decibels louder. At WOP sounds good but not a real noticeable difference from stock h pipe. Does increase torque and horses, I can tell by pedal feel. The high flow cats work good, only put about 500 miles on them and no issues yet. Having an expensive h box like this has really made me consider changing my cat back to like a competition or track cat back like borla attack of manga flow competition. Overall giving it a 4 because everything about it was okay and did add some horses and torque, but was just quiet and not noticeably deeper than stock.


      Year: 2002 Submodel: GT

      Helpful (9)

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