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Kooks 1-5/8 in. Header and Off-Road X-Pipe Combo (99-04 GT)

AmericanMuscle no longer carries the Kooks 1-5/8 in. Header and Off-Road X-Pipe Combo (99-04 GT). Please check out 1999-2004 Mustang Exhaust Combos for an updated selection.
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Features & Details

  • Increase Rear Wheel Horsepower and Torque
  • Includes Long Tube Headers w/ Matching Off-Road X-Pipe
  • 304 Stainless Steel Construction
  • For Off-Road, Track Use
  • Free Flowing Mandrel-Bent Tubing
  • Fits 1999-2004 GT and Bullitt Mustangs
Improve Horsepower And Torque. The Kooks Long Tube Header and Off-road Shorty X-pipe combo kit for the GT and Bullitt Mustang will balance out the exhaust pressure to increase flow over the restrictive factory exhaust system resulting in more horsepower, torque, and better throttle response.

Quality Construction. Manufactured from 1-5/8" mandrel bent 304 stainless steel tubing Kooks Long Tube Headers are TIG welded for strength, and feature a leak-free ball flange design to fit perfectly into the included 2.5" diameter 304 stainless steel Shorty X-pipe for excellent exhaust flow and performance.

Natural Finish. These Kooks Headers feature a natural stainless steel finish, which provides an aggressive appearance to your engine bay. This is not a heat-resistant coating, AmericanMuscle recommends the use of Exhaust Heat Wrap for high performance applications.

Recommended Upgrade. To realize the full power potential that this Kooks Long Tube Header and X-pipe Kit has to offer, AmericanMuscle recommends a custom tune with a Mustang Handheld Tuner to reprogram the vehicles computer (ECU) for proper operation.

Application. This Kooks Long Tube Header and matching off-road shorty X-pipe combo kit is designed specifically for the 1999-2004 4.6L GT and Bullitt Mustangs.

Technical Note: This Kooks 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



CA Residents: WARNING: Cancer and Reproductive Harm -

What's in the Box
  • Kooks Long Tube Headers
  • Kooks off-road shorty X-Pipe
  • Necessary Gaskets
  • O2 Extensions
Installation Info
Tech Specs
Will it fit my Mustang?

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Questions & Answers (5)

5 Top Rated Questions

This is designed for catback only, correct?

  • Yes, this kit is designed to be used with a cat-back exhaust system.

Helpful (0)

Will this kit fit my 04 mustang gt with automatic transmission

  • These Kooks 1-5/8 in. Header and Off-Road X-Pipe Combo can be installed on any manual or automatic transmission 1999-2004 Mustang GTs.

Helpful (0)

Will this setup work with slp loudmouth exhaust? And does it come with gaskets and hardware?

  • So because this system is designed to fit with the stock catback and the SLP catback is designed to fit with the stock midpipe, it would be safe to assume they are indeed compatible with each other! I will post the link to the SLP catback below:

Helpful (0)

Will the shorty x-pipe fit with my borla stingers?

  • The shorty X-pipe in the Kooks header and Off-Road X-pipe combo will work with the Borla Stinger exhaust.

Helpful (0)

Will this fit the Manual coupe?

  • This system fits a manual or automatic car

Helpful (0)
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Customer Reviews (7) Write a Review

Overall Rating 4.9

out of 5 stars

Installation Time:Weekend

Installation Cost:$500-$1000

  • Performance Gain 4.857143 4.9
  • Fit 4.714286 4.7

  • 5/5

    Installation Time: Shop Install

    Installation Cost: $250-$500

    March 26, 2018

    Kook headers and o/r x-pipe combo set

    Amazing product! I recommend you get this combo you want regret it! Amazing sound and doesn’t get any better than Kooks. Bet headers and x-pipe combo to have in my opinion.


    Year: 2004 Submodel: GT

    Helpful (7)

  • 5/5

    Installation Time: Weekend

    January 08, 2018

    best exaughst

    it was a hard as heck install but you feel a good diffrence in power


    Year: 2004 Submodel: GT

    Helpful (7)

  • 5/5

    Installation Time: Shop Install

    Installation Cost: $500-$1000

    July 29, 2017

    Sounds awesome!

    Would recommend this to anyone sounds really loud especially since I have it with the borla attack exhaust and you can feel the power when you get on it. My mechanic charged me $500 I know most shops charge around $800


    Year: 2004 Submodel: GT

    Helpful (8)

  • 5/5

    Installation Time: Weekend

    July 10, 2017

    Sounds Amazing!!!

    I have the Borla Stinger S Catback. These Headers made my exhaust sound amazing. Great Muscle car growl. I would recommend them for anybody.


    Year: 2004 Submodel: GT

    Helpful (9)

  • 4/5

    Installation Time: Weekend

    June 22, 2017

    Looks headers

    Best sounding exhaust I've ever heard. worth the head ache was about a 10 hour install had the motor out doing other work though made it easier was a little disappointed that the o2 sensors didn't fit between header and auto trans had to relocate them and was told from the manufacturer that they wouldn't got because the headers were designed stupid a powerglide which was stupid because those were never put in a mustang but over all very glad a did it


    Year: 2001 Submodel: GT

    Helpful (6)

  • 5/5

    Installation Time: Weekend

    June 20, 2017

    Long tube Kooks

    Kooks makes a first class header very difficult installation


    Year: 2004 Submodel: GT

    Helpful (7)

  • 5/5

    Installation Time: Weekend

    May 14, 2013

    Great sound and horsepower gain.

    Installed on a 2003 Saleen S/C Car. Installation was crazy and almost impossible because of absolutely no clearance but after a whole lot of persistence they are finally installed. Without having it tuned yet I could feel the Horsepower gain and the sound is awesome. Would definitely recommend these headers and x-pipe but plan a weekend or longer for install.


    Year: 2003 Submodel: Other Chicago, IL, USA

    Helpful (12)

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