I had a the same issue, the shop put a new belt on and I had a noise issue soon after. To fix the problem I ordered a new idler wheel, and tensioner. I spent 4 hrs installing them but the true root cause was excessive play in the idler pulley shaft / wheel compared to the new one. Having just bought the car in june 2011, I can not vouch for it's history but the car has 350,000 km on it and replacing these parts was on my list of to do's anyway. bty 87 300 dsl , good luck Cheers Dave D.
ps added photos in gallery, of eng. bay

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