I have a 230 SL with 250 head and later model fuel injection pump. Ive cleaned the fuel tank, replaced the fuel pump, replaced the fuel filter, replaced the spark plugs with a higher temp model (due to buildup). Engine is running rich but mechanic has been unable to fix. Cold start valve appears to be ok. The engine will stall after hard excelleration if gas pedal is released. Thereafter engine is hard to start (as if no fuel) pumping gas pedal help start. Once started engine runs ok. Any help would be appreciated. Thanks Chuck