When I eliminated the air pump on our 96 F250 gasser I rerouted the belt in such a way the idler pulley was eliminated. It was not my plan but it worked out that way. Now several months later there is a lot of squealing when the truck is running. I believe it is the pulley on the pensioner I just have not gotten enough free time to check it out and repair it. Anyhoo, I am wondering how necessary the idler is. My wife had two idler pulleys fail on her two separate times when she was out of town and I was overseas. So to me they are just one more thing to have to repair or replace. Any input on that?