Changing the belt tensioner cured my squeal. Another thing I did, was take a wire brush to every pulley that was grooved. I believe they are: the crank, alternator, a/c and power steering. Rubber from your old belts will tend to build up in the grooves and you will have rubber to rubber contact. I have yet to buy any belt treatment that worked for very long. Don't waste your money on any of them. IMO!! The cam positioning sensor will also make you think it is you belt. If you have the 3.0 v6, it is located at the back of the engine and on the passenger side. Hard to see, but you can listen to see if the squeal is coming from there and not the belt. If you still think it is the belt, try spraying WD40 on the belt, w/ the engine running, and see if the squeal goes away. If the squeal stops, then we can forget about the cam positioning sensor for now and concentrate on the belt area.