Killer B Motorsport 4-1 Holy Header 2-Bolt Subaru WRX 2002-2014 / STI 2004-2021 | HH-2BOLT

Part #: HH - 2BOLT. The Killer B Motorsport Holy Header is a top - notch exhaust header crafted using advanced CAD software and simulations. It's designed to boost power in the mid to high RPM range. With short primaries and a single secondary, it significantly reduces header volume, allowing exhaust gas pressure to build up quickly. The symmetrical 4 - 1 design keeps exhaust velocity high and consistent as RPMs increase, leading to faster spool - up compared to long primary/double secondary designs. You'll instantly notice improved throttle response and better power at higher revs. **Key Features:** - Short Equal Length Primaries: The shortest possible on an Equal Length header, meaning less volume and quick spool - up. - Symmetrical Primary Design: All primaries have similar tube length and bend geometry, maintaining high and consistent pulse velocities. - Smooth Mandrel Bends: Utilize mandrels for smooth, non - restrictive flow and the largest bends at every location for optimal performance. - Thick - Walled 321 Stainless Steel Construction: Alloyed with titanium, it's ideal for high - temperature turbocharged applications, offering better strength and toughness than 304 stainless steel. - High Heat Retention: Conducts less heat than 304 stainless steel. Short primaries and properly sized secondaries increase turbine efficiency. Can be ceramic - coated or wrapped without exceeding temperature limits. - Lightweight: Weighs only 17 pounds compared to the OEM's 25 pounds. - Compatibility: Works with OEM EJ25 Oil Pans and Killer B Motorsport Performance Aluminum Oil Pan. Also works with any 2 - Bolt Up - Pipe, including rotated ones. Note: Up - Pipe is not included. **Fitment:** - 2002 - 2014 WRX - 2004 - 2015 STI - 2004 - 2014 Forester XT - 2005 - 2009 Legacy GT - 2005 - 2009 Outback XT **Modification Notes:** - May need slight modifications to the stock oil cooler for 06 - 07 WRX and Forester XT models. - Some models may require modification to the stock fan shroud. - 02 - 05 WRX may need a 2.5l STI oil pan. - 06 - 07 WRX requires an STI oil cooler and STI oil pan. **Legal Notice:** NOT LEGAL FOR SALE OR USE IN CALIFORNIA ON ANY EMISSION CONTROLLED MOTOR VEHICLE.

Using the Killer B Motorsport Holy Header is straightforward. First, make sure your vehicle is in the fitment list, which includes 2002 - 2014 WRX, 2004 - 2015 STI, 2004 - 2014 Forester XT, 2005 - 2009 Legacy GT, and 2005 - 2009 Outback XT. Keep in mind that some models may need modifications to the stock oil cooler or fan shroud. You'll also need to check if your specific model requires a different oil pan, like 02 - 05 WRX may need a 2.5l STI oil pan and 06 - 07 WRX needs an STI oil cooler and pan. The header works with OEM EJ25 Oil Pans and the Killer B Motorsport Performance Aluminum Oil Pan, as well as any 2 - Bolt Up - Pipe (but the up - pipe isn't included). When it comes to maintenance, since it's made of thick - walled 321 stainless steel, it's quite durable. You can ceramic - coat or wrap the headers to improve heat retention, and it won't exceed the temperature limits like 304 stainless steel. Just remember, this product is not legal for sale or use in California on any emission - controlled motor vehicle.