couple questions for a 94 sse

ok this problem started a few months ago.... Very rarely I will start up the car and it will sound like shit.... I dont really know how to explain this but the engine doesnt seem to be firing correctly...... ummm lets see, it just doesnt really run smooth, very rough, it will stop once I gun it and drive till about 40-50mph. Sorry I couldnt give better details but thats all that I came up with.

My bonny has 196000 on her... orig. engine different tranny replaced at who knows what mileage. Ok this is another confusing questilon. Sometimes she will run perfectly, as in when I hit the gas she will take off, other times shell seem not to be so good at acceleration or anything else. I guess what I mean is a intermittant loss of power. Any suggestions? Sorry I couldnt be better with the details

Heres whats been done to the car within the last 15000 miles

2 tuneups (plugs/wires/PCV valve)
Air Filter twice
Breaks
Bearings
Alternator
4 Oil Changes
Hoses to throttle body
Crank Sensor
Water pump
Acc. Belt
Power Steering cooler
Rims (stock rims from a 95 Grand Prix that are same standards as Bonny)
Tires (at correct PSI as well)
L&R ball joint
L- CV Joint
Alternator
MAF sensor
R air struts
air compressor


I believe that is all.... I do too much damn work to that car haha. Well Im pretty sure thats all ive done to it..... actually now that I look at that list I realize ive done too much to it lol. Well it wouldda been a lot more taking it somewhere and having it done!!!