Mercedes: starting my car, piston rings, oxygen sensor

Question
i have a 1987 me-be 300e w/fuel injection. after i start my car, i must rev the car abit, at least 45 seconds or more before the engine smooths out. i took your advice and had new piston rings and distributor cap and rotor put in and the car must wait awhile before its idling smoothly. is there something i overlooked? thanx for your cooperation!  dan williams

Answer
Any of the following units can effect startup idle.
The tough part is; it can be a combination of them.

Air Temp. Sensor
Altitude Sensor...
Cold Start Valve
Cold Start Valve O-Ring
E.H.A. Valve
E.H.A. Valve Seal
Fuel Distributor O-Ring
Fuel Injector Seal...
Idle Control Valve
Oxygen Sensor
Throttle Body Gasket
Water Temp. Sensor...

Hands on diagnosis by a MB master technician may save you big dollars here.

The simple answer could be a couple of marginal spark plugs, are you running copper or platinum??
Is old = bad fuel possible???