Mercedes: 78 450 SLC IDLE SCREW, vacuum leaks, mercedes benz

Question
I HAVE A 1978 MERCEDES BENZ 450SLC.  THE ENGINE IDLES HIGH BETWEEN 1500 AND 2000 RPM'S.  SOMEONE TOLD ME THAT THE MERCEDES BENZ DEALERSHIP NEEDS TO ADJUST THE IDLE.  IS THIS TRUE OR IS THERE AN IDLE SCREW LOCATED ON THE CARBORATOR AND IF SO, WHERE IS IT AT?   THANKS

Answer
How many miles on the car?
What other symptoms?
Black slime from exhaust?
Oil used  between changes?
What is current MPG?
How is snap throttle response?
Are there any vacuum leaks?

Suggest you replace the ignition coil if it is factory still, they die slow and cause many issues as they get weaker.