The fuel distributor from a 420/560 is different for a 380SE. Also, I dont believe you can do a valve adjustment on your car. They are hydraulic. I could be wrong though. Check your intake gasket. Does the idle get better when the car is warm? Try to narrow it down some more.
93 300D 2.5 Turbo, Black/Palomino 273K
09 E350 Black/Black 41K