My 1977 280E seems to have a miss in it when it's hot. It's got new gas, new plugs and plug wires. Has Electronic Ignition. Fires up pretty easily but idles fast until it's put into gear, emmits a lot of smelly smoke (white/grey). Engine seems to stumble more when it's accelerated. Car sat for a 2 years before I got it. Could this be something with the vacuum system? Is there something that controls the idle speed as engine warms up and the engine timing that might have a leak or rotted off? Overall engine runs well except for the misses you can hear and the quality of the exhaust.