Has anyone out there run into a squealing sound (it sounds like a fan belt squeal) only when letting off the gas. It does not squeal when accelerating or held the at a constant speed. The squealing is intermittent and tends to happen most when the car has been driven for an hour or two. I cannot get it to squeal while it is in park or neutral -  that would be too easy 

I have changed the generator and belt (for other reasons) and have taken off the power steering belt. I have also oiled the distributor and water pump.

The squealing also goes away as soon as I stick the car in neutral as it is slowing down. It sounds like it might be a vacuum leak however I have checked the hoses and they are on pretty tight.

Any help would be appreciated.