The sound is incredible on my little 4.8L V8 an I couldn't be happier with the purchase. It has a deep growl on start up and during idle, to me it almost sounds like a diesel without the turbo whine. Very quiet in the cab when cruising and absolutely no drone. When you get on the gas you can really hear it open up. As far as performance, it feels like i had some gains especially coupled with my CAI but its to early to tell if I'm getting any extra MPGs. Can't stop mashing the pedal to the floor!