Steve - I have just read your "challenge" - been outside installing a replacement window in the right rear door of a 300SD for a friend (made $50 - took 2 hours
).
Anyway, I know a little something (very little) about industrial controls and instrumentation (I know ALOT about pumps and pumping systems) my GUESS would be that a new - "good" working OVP relay could possibly put the correct voltage to a bad idle speed control valve which could possibly prevent the car from running the way it should. Just my GUESS
I'll bet the majority of diyer's on here thoroughly enjoy this type of "challange", I know I do. First prize should be a free tour of Continental Imports in Gainesville, Fla
whenever the winner is in Gainesville.