The EDS itself rarely fails. It's the sensors and actuators it works with that can drive you nuts because of the rudimentary OBD. I haven't read any worthwhile discussion here about error codes or what the diagnostic steps are given certain codes for that engine. Those that want to preserve the system throw parts at it. Usually vacuum amplifiers. Maybe you can borrow vacuum amplifiers from your buddy. Get your hands on a factory service manual if you don't have one.

Sixto
87 300D