Just installed mine first mod I have done. The turbo whistle is so much fun I took it up a near by canyon just to hear it. I din't think it would be that much different in sound but it was I had a stock box with K&N and holes cut out of the box in the bottom of the box by the previous owner.
Another vote for Tymar, I wasn't sure if it would make a difference but it sure did. Very easy clean install, talked with Dale a few times and he is a great person to deal with, I'll definately be buying more upgrades from him in the future.