Believe it or not here is the latest. I asked around at work and was referred to a shop in Atlanta called Performance Imports which is run by a guy named Peter Wendt (sorry Donnie at MB Autowerks, he was closer and close enough to a Marta stop logisticswise). I explained the whole history to him and he chuckled at what the previous shop had done. He had to take several drives in the car before it acted up. Even though they appeared to be okay with the exception of some evidence of some bleed through on the plug wires, he suggested of all things a cap, rotor, and wires. He also found a leaking water pump bypass hose and collapsed motor mounts but since he realized that I could do it myself, he did the right thing by advising me and not trying to shaft me like so many other businesses do. He also said it could use a set of injectors but it was not that urgent. HONESTY at last. I was going out of town for a month so I asked him to keep the car and use it for a parts runner which he did.
I picked it up last Wednesday and, knock on wood, it runs like a top. Until Friday that is. No it still ran great but was making a clicking sound from under the hood. To make a long story short, I caught the fan from going through the radiator. The bearings had failed behind the fan clutch. I'm replacing it tomorrow and will keep you posted about the drivability.

Owning a 90- 300E with some 170.000 KM's on the charter, I sort of made it my mission to having it run smoothly. It does spin like a cat, but used to start very rough, worse when it had been left for an hour or so.

I read, and certainly appreciate, almost all the good advice in this forum, eliminating theories one by one.

Now I'm close... I really think i've gone a done it now..!

It starts first crank every time, and all I actually did the last time i had the hood up for a couple of hours, was to clean and lubricate the Idle Air Control Valve.

Ever since, I seem to get the right mixture when cranking, untill the CO sensor kicks in and closes the loop.

Anyhow, I'm happy for now, and thank all of you guys for your valuable contributions.