Car in question is a 1992 300E with 129K.

Car will idle at 2000- 2500 RPM once above 80 degrees.

If I unplug the idle control valve idle drops to about 1100 in park and 750 in drive, starts and runs fine.

Problem started after replacing air flow meter boot, idle control valve hoses
which were cracked. Also replaced breather hoses, valve cover gasket, O2 sensor, and all accessible vacuum connectors.

Fuel injectors and seals have also been replaced. Temperature sensors are new. Cap rotor plugs and wires are also new.

Car runs good with new idle control valve unplugged. Plug it back in high returns.
Duty cycle and potentiometer are in spec

Please help I am baffled.

Thanks in advance
Paul