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Kooks 1-5/8-Inch Long Tube Headers with Catted X-Pipe (99-04 GT)

Item 65530
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      Product Information

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


      • Increase Rear Wheel Horsepower and Torque
      • Includes Long Tube Headers w/ Matching Catted X-Pipe
      • 304 Stainless Steel Construction
      • High Flow Catalytic Converters
      • Free Flowing Mandrel-Bent Tubing
      • Fits 1999-2004 GT and Bullitt Mustangs


      Improve Horsepower And Torque. The Kooks Long Tube Header and Catted 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 catted shorty X-pipe combo kit is designed specifically for the 1999-2004 4.6L GT and Bullitt Mustangs.

      Technical notes. Not legal for use on pollution controlled motor vehicles; intended for off road use only.

      Fitment: 1999 2000 2001 2002 2003 2004 Details

      MPN# 11212000


      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (3)

      Write a Review

      Ratings Summary

      5.0 out of 5 overall rating from 3 customers

      Installation Time: Weekend

      Installation Cost: $250-$500

      • March 01, 2019

        5 2001 GT - Roger

        Kooks Sound Great! Can feel the additional power.

        i love my Kooks headers with catted X pipe. I was afraid that they were going to sound raspy with the X pipe as I have read repeatedly to go with an H pipe for the traditional muscle car sound. However, no H pipe was available for my 2001 Mustang GT. I was also concerned about going catted, but my previous exhaust was uncatted and I could always smell the exhaust fumes. These Kooks sound the best I have ever heard. No raspiness at all. A low rumble just like I was hoping for. I have them mated with Magnaflow Street catbacks. Out of the dozens of videos I have listened to, I honestly think my sound better than them all. I have some loss of torque in the low RPM's, but in the higher RPM's the additional power is very noticeable. The low end loss, however, may be due in part to the installation of an intercooler on my supercharger. I highly recommend Kooks.

        Helpful (3)
      • July 14, 2017

        5 2001 GT - Rivera97 Installation Time: Shop Install Installation Cost: $250-$500


        These pipes sound so freaking good at about 3k rpms would definitely recommend for anyone that likes a loud car lol

        Helpful (15)
      • June 18, 2016

        5 2001 GT - Chris2826 Installation Time: Afternoon

        Great Headers

        Great headers, Brought my car from a mumble to a rumble in a matter of hours (Self Installed) I'm glad to open my bonnet and see that shiny chrome.

        Helpful (20)

      Questions & Answers (12 answers)

      5 Top Rated Questions

      Is this compatible with the Borla Touring Cat-Back Exhaust (99-04 GT, Mach 1)?

      • This will work with the Borla exhaust yes.

      Helpful (1)

      will these work with an automatic transmission?

      • yes it would

      Helpful (1)

      After putting this kooks header combo will it need an immediat tune or can the tune wait? Or will it mess up the car if it's not tune right after?

      • It would be best to have your car tuned right away to make sure it is operating properly and does not do any kind of harm to your motor.

      Helpful (0)

      Will this combo work with SLP Loudmouth Cat-Back Exhaust

      • Yes, this would be compatible with the SLP Loudmouth cat back. 

      Helpful (0)

      Will this delete the EGR?

      • Yes, these headers will delete the EGR.

      Helpful (0)
      Post Your Question
      7 More Questions
      Will the kooks LTH X-pipe combo kit pass emissions testing in Texas? 1 answer
      Will this combo work on a 2000 s281 sc convertible with borla stinger cat back? 1 answer
      will these headers require a oil filter relocation? and if i ever need to change the spark plugs after i install these headers, will i need to remove the headers to replace the spark plugs? 1 answer
      If i have buy this combo would it hinder the emmisions for CA? 1 answer
      Will this product work on the borla atak series? 1 answer
      is this combination applicable for borla stingers catback? 1 answer
      Ive herd that puting a 3" piping on a stock 02 gt i would lose power unless i have more mods i judt want to know if that is true? 1 answer

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • Kooks Long Tube Headers
      • Matching Kooks catted shorty X-Pipe
      • Necessary Gaskets
      • O2 Extensions

      Tech Specs

      Header Specifications
      Header Type: Long Tube Finish : 304 Stainless steel
      Type Mid Pipe Required: Kooks Shorty X Fitment: 1999-2004 GT and Bullitt

      Mid Pipe Specifications
      Style Mid Pipe: Shorty "X" Type Headers Required: Kooks Long Tube
      Piping Material: 304 Stainless Steel Piping Size: 2.5"
      Catalytic Converter: "Yes" Fitment: 1999-2004 GT and Bullitt

      Will It Fit My Mustang

      • Bullitt - 01
      • GT - 99, 00, 01, 02, 03, 04

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