Had my 5 throwing a belt yesterday, the prognosis I have come to is that I just didn't have the belt tight enough. All my pulleys are aligned perfectly and the alternator itself doesn't move at all. I've bought a belt jump guide.
Do these make a big difference?? I want to rev upto 7 k. Cause the setup I've got is capable of that all day long
Oh and obviously I changed the belt. Haha.