Mixture problem with a 1980 450sl.

[marty kelly]

Engine starts great from cold, then if hot, would take a good 30 second crank to get it started again. When hot the engine runs rough and rich. MPG is terrible.
I replaced a fuel pump check valve, a fuel accumulator and fuel filter in the hope it would cure a long cranking issue when hot due to suspected loss off pressure. I now need help to get the engine to idle smoothly / set the mixture, no turning of the hex screw makes any difference. Have checked for vacuum leaks, I am wondering now if the warm up regulator is faulty. Any suggestions would be greatly appreciated.