Patented steel construction baffle now features more high-temperature fiberglass packing, provides significant gains in horsepower and torque and exhibits a distinctive, throaty sound. Use all factory mounting hardware. OEM heat shields may be retained. U.S. patent 5,173,576. Made in the U.S.A.. ECM units on fuel-injected models need to be recalibrated if used with free-flowing air cleaners and/or modified engines. Muffler shells may discolor if ECM units are not calibrated correctly.