Just installed the GT500 Axle Backs yesterday and was surprised at how quiet they are. They do have a little throatier sound on acceleration, but at idle and freeway speeds they sound the same as the stock mufflers. I installed them in the driveway on jack stands. Other reviewers mentioned loosening the mid pipes near the center of the car and that is exactly what you need to do to make the install MUCH easier. Took no more than an hour by myself. Great sound and fit but a little tamer than I expected.