my engine is hesitating when I try to accelerate

I have a 1997 Chevy astro with a 4.3. The whole time I'm on the gas it feels like it don't want to go. The way I can describe it is like having a stick shift and going from second gear to fourth gear going too slow. It's a constant vibration sound and annoying as hell. Please help. Also going down the freeway the vibration or whatever noise is so loud I can't listen to the radio while on the gas pedal. Let off, stops