Did he use a screw and poke it into the top of the air cleaner and turn? That will increase/decrease the idle but introduce other problems.

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1992 200E
M102
102.963
AKA Silver Old Grumpy
Always hope I can freeze someone with the aircon- Just change the compressor again, Subseal leaked with a psssssssss sound.
Its the NON-3 Pointed star items on my car that cost more to repair.$%^&%%*^&