Bought a Flowmaster X-Pipe with some rear axles on my 15 Mustang GT. The X replaced the stock resonator and still sounded loud as hell, and there was a lot of rumble on the highway in 6th. I cut 2 of these where the standard was and that solved all my problems. The roar is almost nonexistent, but more importantly, it cleaned up the exhaust noise and removed the rasp. The sound of the Flowmaster without any flaws, exactly what I wanted.