Well, you have spent allot of money and the problem is still there. It can be many things. My guess would be vacuum leak. Replace all vacuum lines, (cheap fix and probably needed anyway due to the age of the vehicle) and see if that fixes it. If not, Stop throwing parts at the problem and take it to a professional and have it fixed. You would be money ahead if you had done that in the first place.
Check for fuel pump pressure; You may have a weak fuel pump. Sounds like a possible plugged catalitic converter?
No
That converter is on the recall list. check it out.
It is inside the torque converter.
No.
check fuel presure and mostly volume, restricted filter? Rick ASE L-1 Master TransMichigan.com
I'd vote for the injectors. Try a professional fuel injection cleaning. Occasionally run it up to 3500 rpm for 30 seconds in low gear to keep breaking up the carbon deposits.
No. The torque converter does not have a drain.
No.
YesYes
if it is an automatic could be spark plugs or spark plug wiring...if a manual check the fuel pump
yes, yes you do