I would double check where your tensioner is at when installed. They have a range they are supposed to be in, and if it was a tight fit, you may be putting too much tension on the pulleys, which could potentially damage them. I ran into the same problem as you and the only option I could find was a tight fit as well, but I still had a little play on the belt so I thought I was good. Well, it actually wound up bending the pulley on the alt, which caused it to break right off. The belt, being intact, didn't just get spit out like a broken belt would. Instead it got wrapped around components, broke the tensioner, destroyed idler pulley, and did some damage to my ground cable, fan shroud, and fuel line. After that, I found out what the acceptable range of travel for the tensioner was and shopped around until I found a belt which put the tensioner in that range.
