Idle speed on my '91 E-34 535i seems too high. Adjustment screws on the throttle body have no effect.?

Question

Throttle Plate appears to be making good contact with Throttle Body. Intake manifold vacuum is ~17.5 inches and steady. Car has Auto Trans. and less than 75,000 total miles. Idle speed needs to come down about 50 RPM to keep car from creeping across the intersections while waiting for a stoplight to turn green.

Answer 1

I believe it's controlled by the ECM which can be serviced by the dealership.
We can't do much on these newer machines w/o a technical masters degree it seems.
Oh how I long for days gone by.

Answer 2

Yeah, take it in or find a shop where they know what they are doing.