1993 Oldsmobile 88 Engine sputters/struggles

Engine Performance problem
1993 Oldsmobile 88 6 cyl Front Wheel Drive Automatic

I have a 1993 oldsmobile 88 royale. Whenever I accelerate from a stop, the engine sputters/struggles if I press on the pedal too much. I have to lightly press it and it takes off and drives ok. While driving, if I press the pedal any further than what I pressed to take off, it also struggles. One time, I pressed the pedal almost all the way down, only to have the same problem, but this time, it seemed to pop, or what I can assume was backfiring. I have changed the spark plugs and wires, the air filter, used injector cleaner, and replaced the fuel filter. Using the ac seems to increase the problem slightly. I have been told it might be the throttle positioning sensor or the speed sensor. I have seen similar questions and sometimes they mention checking the catalytic converter. Is that something only a mechanic can do, or is there a way for the average Joe to check himself?