The "tunnel" function is an option on mostly european versions, when you hold the recirculation switch on itll close sunroof and windows, hold the switch off, everything returns to previous open condition.

Yes, I have held the key in the locked position for an extended period of time, nothing.

As for it being an option, wouldnt it be listed in the option codes? All I've read gives me the feeling that it was installed on all 1992 cali w124s.

A definative answer would be most appreciated, at least I can move on to the next issue.