Ok well I had this same problem with the last stang. After deleting the water pump and adding aluminum underdrives after a while the 890K6 belt from advance that fit pretty tight during install stretches after a few weeks and starts to make noise. On the last stang I just put a belt from a lexus sc430 which was 888 gates and never had a problem again. But for some reason on this one the 890 from advance fits fine. but when I try to use the 888 from gates it doesnt fit. Too short by like an inch. I would love to get a quality 890 belt regardless of price but I cant find one anywhere. Any ideas?