High Pitched Noise

I have a 2000 Trooper, which has most of the problems on this board, but has started making a high piched noise, similar to breakes going bad. But, it only makes this noise when idoling and stops when I press the gas. I'm thinking it may be the belt, but was curious if anyone else has had this problem.

Thanks

If it only does it at idle, it's probably a cracked intake manifold gasket. They can whistle/screech in the area of the vac leak.

G/luck
Joel