2001 GMC Yukon belt noises

I replaced the water pump, tensioner pulley and idler pulley as well as the belt and the car would squeak and chirp from the belt but when I put belt conditioner on it gets much worse like an awful squeal when given any gas. What might be the problem and is it possible that the pulley on the alternator may be bad as to me it sounds like this is the root of the awful squeal after the dressing is applied? Thanks in advance, Derek