Same malfuntion code came up on my '95 C220 (car was
idling rough at startup).
After looking for vacuum leaks found that the air duct
between the MAS and throttle body had completely
worn through where its clamped to the throttle body.
Wrapped it in electric tape and now car's running smooth
as ever. Check engine light hasn't come back on.
Will get the air duct replaced this week.