I am experiencing what I must describe as some what of a "bad gas" feeling coming from under the car. It's as if there is a misfire problem going on. I took it to my dealer, and they say that they can’t find an issue. I know my car and you can feel a distinct difference between the sweet rumble of my LS2 and "this". By the way, they checked for leakes in my exhaust (Corsa) Does any one have any input?