If you want to adjust it yourself, do you know about the hidden MFA function mentioned before?
goes like this...
Switch the ignition on, hold the MFA button in,
Switch the ignition off (still with MFA button held in),
Keep it held in, now start the engine.
This then enters you into the hidden MFA function

Scroll through the function and you will find your engine idle speed.
Use this display to adjust the idle maybe?