i have a 2004 envoy with the v6. It's starting to make a squealing after it rains or heavy dew in the morning. I was told it was the idler pulley. When i went to look for a chiltons manual, only to find they don't make one for the 04-05 envoys, the sales guy told me it was called a belt tensioner pulley. Who is right? Also if I take it on the expressway, the speedomer will some times not fully goto zero when stopping, then on acceleration will make it say i'm doing 100 when i am only doing 55. Any help would be great!!