Did you use any fresh heat conductive compound for the ignition amplifier module heatsink (the metal mount that the module sits on with the four screw holes)? If there isn't any there or much left, apply a new coat. I used leftover heatsink compound from a DIY computer installation. The module uses the car panel as the main passive radiator. I had to replace the original self-tapping screws with slightly larger ones to get the heatsink to fit tight and flush with the panel.

Or it might just be that Hall sensor insulating connector socket on the distributor that's disintegrated. Which is quite cheap to replace.

FWIW, I had to install a new distributor to cure my 1989 740's stalling problem. Turned out to be a bad Hall sensor with a very poor quality repair on it by the PO/PO mechanic. If you're planning to replace the cap and rotor at the same time, it really is more efficient to just buy a factory refurbed unit from FCPGroton complete with rotor and cap. The price differential isn't much from the separate components added up, and the Bosch factory refurb piece was practically brand new.