I was asked to post an obscure 1997 TSB concerning the rough idle I was experiencing in my '91.

It deals with a modified ICV and modified air hose.

The part # are, 13 41 1 433 626 for the control valve,
13 41 1 730 071 for the rubber hose connecting from the valve to the intake manifold.

These are for the M-50 without vanos.

Replacing the parts seemed to helped smooth my rough idle, though it didn't completely eliminate it.

Will