Sounds like you've been over this territory before. Sorry if I'm asking stupid questions, it's always easier to eliminate the easy stuff before getting into less-likely problems.
Have you had the injectors tested? One stuck open can stop the car from running. A really bad vacuum leak likewise. I'd suspect a stuck-closed idle air valve could do that too.
I'd also check the resistance of the most important sensors. Cam sensor is important for spark timing, coolant temp sensor, AFM door sensor & intake air temp sensor for cold starts. The DME will run far too rich on cold start if the coolant or air temp sensors are inaccurate.
IIRC, the '93 has EWS. Swapping the DME might not really get at the problem in that case, unless you've disabled it already. That's out of my expertise to troubleshoot. Do you have any idea if it's functional? I'd assume that if you have spark it's working, but I'm not 100% on that. Sorry that I'm not on more solid ground with e36's, I have an e30.