I had much the same stalling-when-warm issue as you. My car is a 1989 740T. I used to drive it for a while a then call the NRMA (the Aussie NSW equivalent of the AAA) for a tow!

According to the 700/900FAQ, stalling when warm could be due to a bad hall sensor/insulator connector, or the ignition module, or the FI/Noise suppression relay.

In my case, a really bad hatchet job on the hall sensor by the previous owner/mechanic was a big issue and the varying tachometer speed at idle when warm was symptomatic. But since I didn't know if it was going to be the one component or the other, I changed out the FI relay and the ignition module at the same time for peace of mind. Also put in a new distributor rotor and cap plus new spark plugs.

BTW, the position of the distributor as well as how it actually fits into the matching hole in the engine is rather important. I first put it in without checking that the alignment is similar to the old one. Bad - engine misfires/starts for a while and then stops. Since I couldn't remember exactly how the old one fitted, I chose a 'somewhere inbetween' alignment. It's worked fine after that. [This whole exercise took forever since the dist/cap/rotor had to be taken off and replaced and then all over again a few times round, within that horrible confined space at the rear of the engine]

The heatsink or base of the ignition module has to contact the car chassis flatly since it uses the chassis to dissipate heat. It helps that the screws are tight and heatsink compound or paste is used - I had to use slightly larger screws to ensure that this would be so since the old screws didn't fit tightly anymore for some reason. The ignition module is right next to the battery. It's trapezium shaped with a multiwired plug connected to it, and it probably has the "Bosch" brand.

I bought all my parts from FCPGroton.com.

The other thing that I have done, given that mine's a turbo car, is to change out almost all of the old intake/intercooler and vacuum hoses. It helped a lot. Most of the intercooler hoses were soft from oil and heat. The vacuum hoses were literally crumbling. I used as many silicone vac hoses as possible.