Kooks Custom Headers - 2011 Mustang GT - 5.0L 4V Headers and Exhaust 2011 Ford Mustang GT 5.0L Cat-Back Exhaust. Includes 3" mandrel bent "Over the Axle" pipes, with Kooks 3" Oval Race Mufflers and 4" Polished Tips. Made in 304 Grade Stainless Steel.