I am not too sure if it changes the sound at all and I have not started the car with out the X and just them mufflers then with the X and the muffler to compair the difference. Probably be a good idea but we didnt think of doing that at the time. Althow we did start it up with everything off and it was VERY loud. I will try and get a recording of what it sounds like tomorrow from inside the car and most likely a drive by also!