High rpms, bucking/ idling/ stalling and completely loosing power.

Hello, I've been experiencing the same problem with my Aveo
for about 5+ months now.
I have replaced a multitude of different things trying to fix this issue.
The camshaft sensor, map sensor, spark plugs and wires.
Air intake hose, flushed the tranny. None of the above have solved my acceleration issues.
I'm getting so frustrated trying to diagnose this on my own.
Brought it to a mechanic, he's baffled and thought I was crazy for thinking my tranny or that in general thinking my car has issues.
He said everything shifts fine and that it's normal to run around 2,000 rpms.
But he said nothing on how it still accelerates so incredibly slow. When I first bought the car it never accelerated this slow.
Someone PLEASE HELP ME. I'm at my wits end and I don't know what else to do for my Aveo.
Its a 2006, 136,000 miles on it.