jason:

yes, it solved my problem. my idle is steady and the car starts fine.

if your car passed all the checks, why bother with the new relay? i too am firm believer of preventive maintenance, but based on my experience and readings electronic parts are not included. it either works or don't. you just have to pay attention to any abnormalities to your car operation that may be symptoms to failure.

i see you only got 60K on your 89 car. wow, that is still break-in period for MB. cheers.