It could be the belt. I bought a duralast piece of junk from Autozone and it didn't last 100 miles before it started yelling and screaching at me. Replaced with one from Bill J and its happy ever since. I swear I'm never gonna buy another Duralapieceofjunk again. Anyway, you didn't post this to hear me rant so I couldn't tell ya much about the tensioner but theres a good chance its the belt too.
