Car won't accelerate if gas pedal is pushed too far

Could be a number of things. Don't replace any more parts until you find the problem unless you just like spending money in which case continue as you are. I'd have the catalytic converted checked to see if its plugged. Also make sure the spark plugs are in good shape. It's easy to forget about them these days and not change them ever. They do wear out and if they're way far gone they can make the engine act like that. And have it scanned for trouble codes. I know its an old car but there is information being saved in the computer.

I would start with the cat converter and find the problem or eliminate it from the equation.