1997 Chevrolet Camaro loss of power

I have a 97 Chevy Camaro 3800 series base model I think. Any who, when I'm driving it, it is sounding like, wah, wah, wah, and the car is swaying forward and backward in sync with the engine noise. It dose this mostly on hills, by the time I reach the top of hills large or small, I will be moving around 5 to 10 mpg. No matter how far the gas is down. Well, actually kinda seams to be better if the gas is only held down a small amount. Would like some ideas on what would cause this to happen