05 3.9 ls here. Belt started squealing when warm once in i while. So i changed the belt. nothing. Replaced idler pulley. nothing. Now it does it everyday. Sound is coming from the passenger side and usually does it when its warm. Not on the first startup of the day at least. High pitched and loud. Not a constant squeal but more "squeek squeek squeek". It will go away if i spray water on the idler pulley only. tried spraying the belt on the drivers side and on the other pulleys with no help. I have tried silicone spray, wd-40, and penetrating oil. Any ideas would be great. Its driving me bonkers.