Engine Rev' question. HELP! >_<

Hey guys.
I own a 94' Skylark and have had it for about 2 years. Bought it used, now has roughly 145k milage. Never had any problems with the car until recently when EVERYTHING is going wrong. Had to replace heater coil, starter, alternator, brake drums, window motors, etc (not to mention Tons of cosmetic things). Just recently got it back from the shop after having the alternator fixed (which ironnicaly started making noise when the starter started acting up). Now on to my next problem...

I was driving to school today on the backroads (I now feel I cannot trust this car much on main roads). While going under 40mph the engine made an odd sound when I would accelerate. It sounded like a dull whine when I accelerated then a dull winding down when I let off the gas. However it only did it for a minute so I am not sure if it is a fluke or something that is just a warning to a much bigger problem. Engine and transmission appear to be fine, car is not running hot, plenty of oil and transmission fluid. The sound was an loud over-exagerrated sound of when you actually accelerate. If anyone has any idea what this could be, maybe lose belt?, I would appreciate the insight.

You may wanna check the fuel pump, fuel pump relay, or the fuel filter. I would replace the relay and the filter first, they are probably around 20 bucks for both if that doesn't fix it you may have to just buy the whole pump assembly. I have a 92 Skylark GS, and I had a dull while that got louder and happend more often, until it was real loud and on all the time. Turned out to be the fuel pump.