HOW DO YOU CLEAN THE WUR? REMOVE FROM MANIFOLD AND USE BRAKE CLEANER? THANKS FOR ANY INFO

I am not aware of a computer on a 450 SL. This is Kjet CIS, right?
I think you might want to give a thorough cleaning to the WUR.

Is the smoke black (indicating rich condition)?
If the WUR isn't switching from running rich at cold to leaner when warm, you will get symptoms you describe.

Will you pull the plugs to check. Wet black plugs can mean rich.
Also the plunger in the FD, if it is stuck to rich (low control pressure) will blow black smoke.

The fuel passages in the Fuel Distributor and the Warm Up Regulator in CIS cars are tiny and the least bit of dirt and/or rust will affect flow and pressure.

Don't let it run too rich too long. It will mess up the cylinders when the oil washes down.[/QUOTE]