Corolla making strange noises

[Pokes28]

My '95 Corolla has started making a warbling noise when I'm going down the road maintaining a lower speed and it is worse when I just let off the gas completely and let it naturally slow down. Hit the gas or the brakes and the noise pretty much stops. I can't really tell where the noise is coming from while I'm driving.

This car needs to last me another 2 years so I can get my house paid off before getting something new. It has 180,000 miles on it and I'm about to take it in to have the universal belt and water pump changed as a preventive measure.