my 80' 450sl has developed an odd pattern. In the morning, the car runs great and at normal operating temp, the car runs great. However, if I drive the car at all, then park it for any length of time (5 min-5 hrs?) the car runs vary rough and seems like it's loaded up until I can drive it hard and blow out the carbon. It generally "relieves" itself with some dark smoke around the first gear shift then it's fine. Any ideas?