Next time you clean the MAS, DO NOT use compressed air.
Best way to clean delicate items like that is to use electrical contact cleaner ( spraycan ).
It will not hurt anything & does evaporate.
Don't know where the oil is coming from, or why your S/C behaves so strange.
I'm a little bit concerned about all your problems, as I also ha a 2000 C 230 K.
Keep us posted.
