Since this is a serpentine belt setup, grab your various pulleys and tensioners and see if there is any "slop" in the shafts. If there is, it can cause the pulley to be very slightly out of alignment when the belt is tensioned. The result is usually squealing or chirping. Tight/stiff pulleys due to failing bearings are another frequent cause of squeals on a serpentine setup, you're looking for something that's causing drag.