420sel idle/surging issues
 

Hi, i have an '87 420sel that is having a high idle/surging issue. The car intermittently idles around 900-1000rpms when in park and 600-800rpm it doesn't matter if the engine is hot or cold. It also surges in park when cold, once warmed up the surging goes away. Other then that there are no drivibility issues, theres lots of power, no hesitation, no smoke. It seems/feels like something is sticking somewhere. Here is a list of new parts put on the car. New OVP, idle control valve, idle control unit, cold start injector, engine temp. sensor, throttle body was taken off and cleaned, injectors checked for leaks, non found, also had a smoke test done on the vacuum system and no leaks found. Any ideas as to the problem and solution would be greatly appreciated i don't know what to do with it next.

thanks in advance