Mercedes-Benz: Question ?? 420 SEL

i have an 87 420sel that displays a problem. i'd appreciate anyones
positive input.
when the car is cold and just started it does not smoke, but if i sit at
idle for several minutes to warm it up or if i stop for any length of
time while it's still cold it bellows out smoke so thick that that you
can't see through it as soon as i start moving.
if i just start and go this doesn't happen.
it uses no oil and not a lot of transmission fluid between oil changes
(3000 miles).
once warmed up it doesn't do this either.
could anyone give me a tip as to what might be causing this and where to
look for the part that might need to be replaced.
thanks

Probably your valve guide seals are worn....could be the modulator, check
it, but I would bet on the valve guide seals.