I know that typically with electronics (PCBA's) once they're dead, they're dead. I have an 83 500sl that was running great. It sat for a couple of months while I replaced the interior. It doesn't idle bad at all but when pulling away, it stumbles up to about 1600 rpm then it runs smooth and strong. I took the car out on the highway and ran it pretty hard and the problem went away. Car sat for another couple of days and the problem is back. If I just run it around town doesn't seem to matter how far, it never gets any better. Could this post you described pertain to my problem also, or if the OVR is dead would it run bad all of the time. I've checked the plugs, and they appear light brown in color which I would say is proper. Distributor cap and wires are new also. The fact that it goes away intermittently leads me to believe it is fuel system and not electronic. (could it be fuel pressure? But, I find it hard to believe that only hard highway driving would raise the fuel pressure high enough?)
Any ideas would be appreciated.