I gutted the rattle cats in my 2002 Audi S6, but the turbulence from the exhaust blasts was unbearable in the gutted cans. I put these Vibrant resonators in place of the Kats and now they are connected to the resonators, X-pipe and Apr mufflers with straight pipes. It deadened the sound a lot, got rid of that horrible noise from the mid pipe and it sounds great out of the mufflers. It has minimal hum and the design of these resonators is excellent.