Belt squeal.

I installed my 3g alt around 2 weeks ago, after installing the new alt I had a lot of belt squeal. I dont have an A/C in my car I removed it a little while back. I called the guys at paperformance and they said it will go away and it's just the new alt spins a little faster so if theirs slack in the belt it will squeal. With my 2g alt I never had this problem. I was running a 70.5" belt and it snapped because I had it tensioned to close(to avoid belt squeal), so it eventually ate away at the rubber and snapped. Now I have my 71" and it squeals a lot. What could be the problem and will a A/C idler pulley work; if so were can I pick one up?(The belt is tensioned as far as it will go.)
Thx

i dunno how to fix your sqeal, but at upr.com you can get a nice idler pulley.