Unleash the Power. The American Racing Headers 1-7/8 in. Long Tube Headers w/ Catted H-Pipe - was designed specifically to unleash the horsepower inside what's arguably the most amazing hot rod ever - your GT500. This header systems can deliver performance gains by as much as 40rwhp and 40rwtq, and they're made entirely in the USA. Exhaust Sound. These headers produce the perfect muscle car sound - loud and aggressive. Catalytic Converters. The H-Pipe comes equipped with high-flowing 200 cell metallic substrate catalytic converters. Long Tube Design. The headers have a long tube design that's engineered for a 100% leak-free fit. They're manufactured from high quality 304 stainless steel, and feature merge collectors with scavenger spikes and 3/8" flanges with TIG-welded and hand-ported inlets for added strength and an OEM-style fit. No Tuning. These headers do not require tuning or reprogramming of your Mustang's computer to function. Off-Road Only. The headers are NOT CARB certified and intended for off-road use only. Installation. With the right tools and a high level of mechanical experience, proper installation takes approximately 6 hours. Professional installation is recommended. Limited Lifetime Warranty. This product is backed by a limited lifetime warranty against defects in materials and workmanship. See manufacturer's website for details. Application. These American Racing Headers 1-7/8 in. Long Tube Headers w/ Catted H-Pipe will fit 2011-2014 Ford Mustang GT500's.