I've got a 84 380sl which is missing when idling once the engine is warmed up. It seems to be getting progressively worse this summer. Pulled the plugs and they are clean. I'm getting good gas mileage (22-23 mpg on the last two tanks). And when I'm driving the car appears to be running okay (can't feel it missing). It's only when I'm at stoplights that I feel the engine stumbling or missing. There are no problems getting underway once the light changes. Idling rpms are around 5-600 at idle and if I put it in neutral the symptoms diminish as the idling increases to about 650 rpm. The stumbling or missing does not appear to be happening when the engine is cold. Anybody have any ideas on what the issue might be?