Whats your diagnosis?

Well, we are at a loss here with our 1985 380SL. We have gone through 3 fuel distributors and finally got one that seems to work. But.... we have one cylinder that just won't clean up. The plug is really dirty. And the car smokes after sitting at a light, like its loading up. Does any one have any idea what to look at next? Should we pull the top of the motor apart and look into the cylinder? Any suggestions would really be appreciated.

[G-Benz]

Sounds like you have a plug that is not firing properly (in particular, a bad plug wire).

So fuel in that chamber is either washing the cylinder walls, or not getting complete combustion, (hence the plug tip fouling). So the excessive carbon is showing up at the tailpipe.