Strip off the belt and check the individual pulleys for tightness; particularly the alternator pulley. On my PSD kit, the alternator pulley had the wrong size keyway for the alternator shaft and eventually chewed it up with consequent belt wander. If all's well, you'll need a straight edge long enough to lay from the crankshaft pulley to the charger pulley. You can then use this to find if there's a pulley out of line.