My 04 GT has around 550 miles on it, and if you listen VERY closely with everything OFF while you change gears sometimes you can hear an odd noise, think its kinda like a squeak, havnt listened to it an a while though so I really cant remember EXACTLY what it sounds like but I remember thinking TOB LOL.BTW Stang 23456 did an engine light or anything come on when you installed that prochamber, and how loud is it with those delta flows (3 or 2 chambered?), because I was thinking about going with somthing like that (off road X probably) but I did not know if it would through a code or something without the cats, and I do not want anything loud...thanks.