1991 Chevy Camaro RS car would not accelerate when I pressed the gas pedal

1991 Chevy Camaro RS convertible 350 mileage: 89,000. I recently paid $1,072.00 to have my Camaro repaired after it stalled on me on the freeway. It was towed from the freeway after I managed to pull over on the right side of the freeway; the car would not accelerate when I pressed the gas pedal. The repair shop replaced without my consent over $600.00 in parts and repairs. Estimate was approximately $400.00 to replace the O2 and knock sensor. Then they replaced the TPS, rotor and cap, then finally the computer and fuel pump. My car has been running worse than before I took it there, except of course, it accelerates. It accelerates, but with no power. And when I accelerate, it starts to shake, also when I press the break, it also begins to shake and it seems like it is not going to stop. I've taken it back to the mechanic that replaced it, and the first two times he said he could not find a problem with it after putting it in the diagnostic machine, because the "check engine soon" light comes on after a few minutes of driving, this started after it was repaired. This last time I took the mechanic for a spin so he could see for himself the shaking of the car, he said it was the transmission, and would charge me $1,200.00 to rebuild it. I said "no!" I took it to a transmission shop the next day; he drove it and told me it was not my transmission. My question is, although I know I have been scammed by the mechanic shop that repaired my car, can you tell by what I have stated what is wrong with my car with the shaking at accelerating and breaking, and the lack of power at accelerating? Thanks