I agree with the majority here so far on the sound difference between a stock V8 and a V8 with an X-pipe. There is also a suibstantial difference between a stock 4.8is sound and my 4.4i, even though both are V8's. I was at the dealer a while back and a 4.8is started up and lets just say it made me pay more attention than mine does. Also, it may just be my X, but it seems to me that I hear more engine noise/whine than exhaust sound. The X-pipe makes all the difference from the sound clips I have heard. I hope to do this mod soon, personally.