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Pypes Off-Road H-Box Mid Pipe (99-04 GT)

Market Price $419.99 You Save 12% ($50.00)
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  • Item 387278
  • MPN# HFM17

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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
    • Direct Bolt-On Design
    • For Off-Road, Track Use
    • Fits 1999-2004 GT Mustangs
    More Power. Add even more horsepower and torque to your New Edge 4.6L GT by eliminating those power robbing factory catalytic converters with a brand new Pypes Off-Road H-Box. The Pypes Off-Road 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 1999-2004 GT Mustang will not only increase power as a result of its perforated H design within the center chamber, but it also adds 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.

    Required Upgrade. For proper operation and maximum power potential this Mid Pipe will require reprogramming the vehicles computer. AmericanMuscle recommends a Bama custom tune with a Mustang Handheld Tuner to reprogram the vehicles computer (ECU) for proper operation.

    Application. This Pypes Off-Road H-Box Mid-Pipe is designed as a direct bolt-on for the 1999-2004 4.6L GT Mustangs, with either aftermarket short tube headers or the factory manifolds and a dual catback exhaust installed.

    Note. This H-Box Mid-Pipe is 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.

    Fitment: 1999 2000 2001 2002 2003 2004 Details

    What's in the Box
    • (1) H-Box
    • (2) Down Pipes
    • (2) Clamps
    • (1) Down Pipe Sleeve
    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: "No" - For off-road use only Fitment: 1999-2004 GT Mustangs
    Will it fit my Mustang?

    Customer Photos

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    2 Questions / 2 Answers

    Ask a Question

    Will I need to have shorty headers or longtubes?... or does this bolt right up to the stock exhaust manifolds?


    • The Pypes Off-Road H-Box Mid Pipe will bolt right up to your factory exhaust manifolds or a set of shorty headers. This pipe will not work with long tube headers.


    Helpful (0)

    whats is the difference between this pypes h-box pipe and the mac h prochamber pipe? will i see the same performance and sound out of both?


    • The Pypes Off-Road H-Box Mid Pipe (99-04 GT) and the MAC Pro Chamber Mid Pipe (11-14 GT) is just two different manufacturers making the same style mid-pipe. So, considering they are both chambered mid-pipes they are going to have a similar base sound, however of course both Pypes and MAC have put their own special twist on their respective exhaust pieces.


    Helpful (0)

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    Customer Reviews (5) Write a Review

    Overall Rating 4.8

    out of 5 stars

    Installation Time:Afternoon

    • Loudness / Volume 4.2 4.2
    • Exhaust Note 4.6 4.6
    • Fit & Finish 4.8 4.8
    • Bang For Your Buck 4.4 4.4

    • 4/5

      Installation Time: Full Day

      October 12, 2017

      Good midpipe

      Sounds great and no cackle. Only leaks i had were the slip pipes, some red permetex fixed that right up. Took longer to install for me due to a manifold bolt breaking.


      Year: 2002 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      September 10, 2017

      2004 GT with American Thunder 40 series catback

      I did a lot of research and decided to go with this mid-pipe. Really nice piece, great welds, and all necessary clamps. Unplugging the passenger side front O2 is tough, I had everything unbolted and moved the OE h-pipe slightly to the left and that provided enough room to unplug it. Once out, everything went smooth on the install except those hard to reach O2 plugs. Helps with a 2nd set of hands. So the sound - sounds awesome, very deep, glad I did the install.


      Year: 2004 Submodel: GT

      Helpful (2)

    • 5/5

      Installation Time: Afternoon

      September 16, 2016


      Nice mid-pipe, great quality! Quieter at idle (great for those that don't need to be "loud" 24/7), but...has a nice deep growl, one that definitely lets folks know you are there, on throttle. The Pypes H-box pairs great with my Borla-s catback. Stainless and a nice deep muscle car note? yes please.


      Year: 2002 Submodel: GT

      Helpful (4)

    • 5/5

      Installation Time: Afternoon

      June 01, 2016


      I love the sound! I combined it with Magnaflow catback and it has a nice low rumble at idle. Would be nice to know what Flowmasters sound like with this mid-pipe It's fairly quite until you open up the throttle and then it lets a roar that will make you smile :) I also felt a noticeable gain especially at higher speeds. High quality, looks nice and overall easy install.


      Year: 2004 Submodel: GT

      Helpful (4)

    • 5/5

      Installation Time: Less than 1 Hour

      April 20, 2016


      All I could say that this bad boy make my Exhuast a pantie dropper.! I have it paired with a set of flowmaster super 10s.


      Year: 2003 Submodel: GT

      Helpful (2)

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