My '84 380SL is missing during idle when the weather is hot and occasionally just stops.(seems to lean) During the colder periods, the engine blows black smoke out during startup but clears and runs well after about a minute.(seems to rich) While driving the car seems to run excellent. I've taken it to a mechanic who has changed the plug wires, distributor, rotor and 'adjusted' the fuel/O2. No luck. After research on newsgroups, could this be the control pressure regulator (warm-up regulator) that is the real culprit here and is there something I can do short of just replacing it on a guess???