1999 V6 Passat Belt Squeling

The serpentine belt was changed two weeks ago on my 1999 V6 Passat (101,000 mi) and I noticed a squealing sound coming from the belt area. Brought it back to the shop today. They thought it was the tensioner but when it was replaced the squealing was still there. Don't know if its from the serpentine belt replacement but it sure seems coincidental. The timing belt and water pump was changed at 55,000 mi. so I don't think it was caused by either one of these. The shop thought a new serpentine belt might be needed in case the one installed last week was defective (bad tooth or something similar). The pulleys supposedly have little or no play so I have no idea what it could be and this sounds like a money pit in the making. Any suggestions on potential causes? By the way, should I keep the new tensioner anyways since I plan on keeping the car another 3-5 years. Thanks.

Might be from the alternator or power steering pump. I dont think there is any other idler pulleys for the v6 that would make noise. WNy did you replace the t-belt/ w-pump aty 55k? thats a little early