4-into-1 Exhaust Header

It utilizes an innovative 1.5 to 1 unequal length runner design, which provides the distinct boxer rumble at lower RPMs while still delivering the performance benefits of an equal length setup at higher RPMs. The header features a 4-into-1 low-angle merge cast collector and single-piece mandrel-bent tubing to ensure smooth, restriction-free flow throughout the exhaust system. This header is designed to deliver substantial power and torque gains, with reported increases of +25hp and +25ft/lbs of torque over stock when compared to the factory manifold. It also offers the quickest spooling among aftermarket headers, outperforming the competition. A significant benefit is that no tune is required for installation, making it a safe bolt-on upgrade. Constructed from full 304 stainless steel with 1/2" flanges and 14ga runners, this header is built for extreme durability. Specific fitment details include 2004-2021 Subaru STI, 2008-2014 Subaru WRX, and select Forester XT, Legacy GT, Outback XT, Baja XT, and earlier WRX models. However, certain models may require additional modifications or parts such as an STI oil pan, pickup, oil cooler, or relocation of the oil cooler/filter. Fitment considerations include: - 02-05 Subaru WRX 5MT requires an STI Oil Pan and Pickup. - 06-07 Subaru WRX requires an STI Oil Cooler. - 04-08 Subaru Forester XT requires an STI Oil Pan, Pickup, and Oil Cooler. - 04-06 Subaru Baja XT requires an STI Oil Pan, Pickup, and Oil Cooler. - Some Forester XT, Legacy GT, and Outback XT models are unconfirmed and may require further modification.