I have a comptech exhaust with test pipes & dc sports headers.At the end of acceleration or on suddenly letting off the throttle it emits a bzzzzzz/buzzing bee sound.My mechanic said it might be from not having any cats.There is also a small(4 " ) dent in the middle of the cannister on the muffler.I thought maybe this could have something to do with it.Has anyone else experienced this?Is it normal?Insight would be appreciated as this bumblebee sound at the end of such an aggressive note is driving me insane.