The factory exhaust manifolds on your GTO are one of the first restrictions holding back your LS1 or LS2. This complete full kit pairs Speed Engineering's 1-7/8" longtube headers with a 3" off-road X-pipe that connects directly to the existing axle-back location — replacing the restrictive factory exhaust manifolds and mid-pipes with a free-flowing stainless system designed for significant horsepower gains, an aggressive exhaust tone, and long-lasting durability. Dyno proven to deliver over 25 rear-wheel horsepower over stock.
Built from 304 natural stainless steel with mandrel-bent primary tubes, CNC-machined flanges, and full TIG-welded construction.
⚠️ Important Note: Rear downstream O₂ sensors are not used. A check engine light for catalyst efficiency will appear and must be disabled via PCM tuning.
Kit Includes:
- 1 Pair of 1-7/8" Stainless Longtube Headers
- 1 3" Off-Road X-Pipe / Connection Pipe
- 1 Set of Zinc-Coated Header Bolts (upgrade to stainless ARP bolts available at checkout)
- 2 MLS Exhaust Gaskets
- 2 O₂ Sensor Extension Harnesses
Optional: Speed Engineering LS Spark Plug Wires and Plug Wire Fire Sleeves can be added at the time of purchase.
Features:
- Full 1-7/8" Port-Matched Primary Tubes — Maximum flow from cylinder head to collector for aggressive LS performance
- 3" Collector — Optimized for strong low-to-mid RPM torque
- Mandrel Bent Tubing — Consistent tube diameter through every bend; no crimping, no restriction
- CNC Machined Flanges — Precision fit at the head and collector for a leak-free seal
- 304 Natural Stainless Steel Construction — Corrosion resistant, heat tolerant, and built to last
- Longtube Header Design — Maximum scavenging efficiency vs. shorty or mid-length headers
- Standard Graphite Manifold Gaskets Included
- Dyno Proven — 25+ RWHP gain on GTO applications
- Compatible with 5.7L LS1 and 6.0L LS2 Engines
Vehicle Applications:
Pontiac GTO — LS1/LS2
- 2004 Pontiac GTO — 5.7L LS1
- 2005 Pontiac GTO — 6.0L LS2
- 2006 Pontiac GTO — 6.0L LS2
Frequently Asked Questions:
Q: Will I get a check engine light after installing this kit? Yes. The rear downstream O₂ sensors are not used with this system, which will trigger a catalyst efficiency code. This must be resolved through PCM tuning and cannot be cleared by simply resetting the ECU.
Q: What is included in this kit? The kit includes a pair of 1-7/8" stainless longtube headers, a 3" off-road X-pipe, two MLS exhaust gaskets, two O₂ sensor extension harnesses, and zinc-coated header bolts. An upgrade to stainless ARP bolts is available at checkout. Speed Engineering LS spark plug wires and plug wire fire sleeves can also be added at the time of purchase.
Q: What engines are these headers compatible with? These headers are compatible with the 5.7L LS1 found in the 2004 Pontiac GTO and the 6.0L LS2 found in the 2005–2006 Pontiac GTO.
Q: How much horsepower do these headers add? Speed Engineering's 1-7/8" longtube headers are dyno proven to add over 25 rear-wheel horsepower on GTO applications compared to stock exhaust manifolds.
Q: What material are these headers made from? 304 natural stainless steel with full TIG-welded construction and CNC-machined flanges.
Q: Are these headers street legal? No. These are race-only headers intended for closed-course competition use only. Installation on a street-driven vehicle may violate the Clean Air Act (42 U.S.C. 7522(a)(3)).
⚠️ Race Use Only: This product is manufactured and sold for installation on vehicles used solely for competition. Once installed, the vehicle may not be used, registered, or licensed for use on a public road or highway. Installation on a street-driven vehicle may violate the Clean Air Act 203(a)(3), 42 U.S.C. 7522(a)(3).
