Kooks 11-14 Ford Mustang GT 1-7/8 x3 Header & Catted X-Pipe Kit

Maximum Flow, Full Emissions Compliance: Long Tube Power Without the Compromise

The Kooks 1141H420 1-7/8-inch long tube headers and GREEN catted X-pipe kit delivers the complete bolt-on exhaust upgrade for 2011 and 2014 Ford Mustang GT models with the 5.0L Coyote V8, replacing factory manifolds to unlock dyno-proven gains of 55 and 70 rear-wheel horsepower and 50 and 65 lb-ft of torque through equal-length primaries, merged collectors, and a high-flow 3-inch x 3-inch x 2-1/2-inch OEM GREEN catted X-pipe that connects directly to the factory exhaust for seamless integration and unrestricted flow from idle to redline.

Handcrafted from T304 aircraft-quality stainless steel with 3/8-inch laser-cut flanges, full TIG welds, and 400-cell metallic substrate GREEN catalytic converters, this system supports over 850 HP while remaining 49-state emissions compliant and preserving the Mustang GT's aggressive V8 soundtrack without drone. The precision design maintains factory ground clearance and heat shielding for daily-driven performance cars.

For 5th-gen Mustang GT owners who demand championship-level performance with street-legal reliability, the 1141H420 kit is the race-winning, complete bolt-on solution trusted by Coyote enthusiasts worldwide.

Key Features

• 1-7/8-inch equal-length mandrel-bent primaries for maximum scavenging
• 3-inch x 3-inch x 2-1/2-inch OEM GREEN high-flow metallic catalytic converters
• Full T304 stainless steel with TIG welds and 3/8-inch flanges
• Merged collectors for optimal exhaust velocity
• Direct bolt-on to OEM exhaust no cutting required
• Dyno gains of 55 and 70 RWHP and 50 and 65 RWTQ

Product Notes

• 49-state EPA compliant not for sale or use in California or CARB states without exemption
• Fits 2011 and 2014 Mustang GT coupe and convertible with 5.0L Coyote
• Includes O2 extensions and all necessary hardware

California Proposition 65: Contains chemicals known to the State of California to cause cancer or reproductive harm.

Warranty: Limited lifetime on stainless construction and 25,000 miles on catalytic converters to original purchaser.

Installation Notes

• Professional installation required lift and exhaust experience needed
• Remove factory manifolds and bolt headers to cylinder heads
• Connect catted X-pipe to collectors and OEM mid-pipe
• Torque flanges to 25-30 ft-lbs and run drive cycle for ECU adaptation

This Part Fits

Note: Fits all 2011 and 2014 Mustang GT coupe and convertible with factory exhaust. Manual or automatic.

What's Included in the Purchase

• (2) 1-7/8" x 3" Long-Tube T304 Stainless Headers with Merged Collectors
• (1) 3" x 3" x 2-1/2" OEM GREEN Catted Stainless X-Pipe
• Gaskets, Stage 8 Locking Bolts, Clamps and Hardware
• O2 Sensor Extensions
• Detailed Installation Instructions
• Part Number: Kooks 1141H420

Why Choose Kooks?

• Over 60 years of championship-winning exhaust engineering
• Handcrafted in the USA from T304 aircraft-quality stainless steel
• Limited lifetime warranty and dyno-proven performance

Frequently Asked Questions

• Q: Does this fit my 2012 Mustang GT automatic?
  A: Yes, direct bolt-on for all 2011 and 2014 Mustang GT manual or auto
• Q: Will it cause a check engine light?
  A: No, GREEN cats and extensions maintain proper O2 function
• Q: How loud is it?
  A: Aggressive V8 roar at WOT, refined and drone-free at cruise
• Do Kooks headers require a tune after installation?
  Yes. A professional tune is strongly recommended after installing long tube headers. The significant improvement in exhaust flow changes air fuel ratios and requires ECM recalibration to achieve optimal power output and safe operation.
• Will these headers void my factory powertrain warranty?
  Under the Magnuson-Moss Warranty Act, a manufacturer cannot void your vehicle warranty simply because you installed an aftermarket part unless they prove the component directly caused the failure. Consult your dealer for specifics on your situation.
• Q: Do these Kooks headers require a tune after installation?
  A: Yes. A professional tune is strongly recommended after installing long tube headers. The significant improvement in exhaust flow changes air fuel ratios and requires ECM recalibration to achieve optimal power output and safe operation.
• Q: Will Kooks headers void my factory powertrain warranty?
  A: Under the Magnuson-Moss Warranty Act, a manufacturer cannot void your vehicle warranty simply because you installed an aftermarket part unless they prove the component directly caused the failure in question. Consult your dealer for specifics.
• Q: What warranty does Kooks provide?
  A: Kooks products are backed by a limited lifetime warranty to the original purchaser against defects in materials and workmanship. Racing and competition use applications may have specific warranty exclusions. Contact Kooks Performance directly for warranty details.

Shipping & Handling

• Method: UPS or Fed Ex Ground.
• Availability: Typically ships same day or next if in stock.
• Packaging: Heavy-duty box with foam protection.