1996 Oldsmobile Cutlass Acceleration issues

Hello. I drive a 1996 cutlass supreme 3.1L V6 FWD automatic car with 114,000 miles. Recently (as in within the last 2000 miles), I had the head gaskets replaced, intake gaskets, timing chain, and a few other things. It also recently had a tune up, and a fresh oil change. All fluids topped and everything seems to be ok. Now the problem. When I'm driving, specifically accelerating, my engine will stay at the same rpm, but all power just drops and it just maintains speed even at 3/4 throttle. To get it to speed up, a have to go 100% throttle and it finally "kicks" back in and I accelerate again. This problem also existed before I had all of the work done. Why does my car just cut power like this? I am somewhat mechanically inclined and do have the tools to test most sensors, wires, etc.