Help! My nightmare needs troubleshooting!
 

Heres the story...
Last summer I took my 83 928 to take its emissions test. (why an 83 needs this still is beyond me) It was a humid, 94 degree day, which made me nervous because I dont like to sit in lines running the temp up with no cool air in sight. I finally get my turn at the dyno and the temp gauge is almost in the red, so I'm glad to be running some air through it. Sadly, the technician is a complete hillbilly, who cannot figure out that the shift pattern is not like a mustang or camaro. He keeps missing 1st gear and trying to run the test in 3rd, I watch in horror as he sputters and coughs and almost stalls during the test at least 4 times, all the while staring at the gear pattern on top of the shift lever. I am practically screaming through the window that he isnt in first!! He was actually in 5th a couple times too... Needless to say, the car fails the test. So then I have to buy a 60-day extension, during which time I'm supposed to retest. yay! I pull out into the testing center lot and park, shutting off the soon-to-be-overheating car and go into the office to get the 60-day pass. I'm not happy. when I return to drive home, I start the car, and its running like crap, low idle, no power at all, almost no throttle response unless I flutter the pedal, waiting for it to run smooth. It dosent stall, but wont rev up either. Its running on all 8, not firing out of sequence , no smoke, just what seems like ignition issues... I just changed the O2 sensor, thats not an issue, wires are fine, this has been a well-maintained car... MAF? Ignition module burnt up? something is fried somewhere... please help...

I'd pull the timing belt covers and align everything at TDC to make sure both cam sprockets are still in time.
Quick and easy to do and all it takes is a sprocket to jump one tooth to give the exact symptoms you're experiencing.

Fix the overheating problem as well, most likely the Fan Clutch. How old are the plugs and wires? Replaced all Vacuum Lines? Put your MY info in your Signature, so we don't have trouble remembering what you have.

do you have the smog report. some of the readouts could help diagnose mixture a bit. sounds like its running pretty lean to me.