I have a flowmaster exaust on my 6, i really didn't like it at first, i got a glass pack under the drivers seat, so it quieted it down a lot, it was way too loud, and it would shake the car, and would vibrate the little plates that are suposed to make a vacume and make a ton of horsepower. I put the glass pack on and it sounds great now, but it is kinda wierd to have two mufflers and my car is a lot louder than it origianally was.