On my 1988 240GL, which has a Bosch fuel injection system, I have noticed that there is a brass coloured screw set in the throttle body close to the idle speed adjustment knob. I can't locate what this screw is for from the Haynes manual, it seems to be associated with the idle adjuster. Is it some form of jet for the idle adjuster? Can anyone help and advise if the screw needs to be periodically removed to enable cleaning and proper operation of the idle speed. Cheers Phil