I can't remember if this is with the swords on the E32's or if you can also do this with the throttlebody, but here goes. Basically, disconnect the electrical connector to the throttlebody. Apply 12V of power to the throttlebody power and earth leads and it should come open fairly fast if it doesn't need to be cleaned. If it seems to open slowly or stick in certain spots, open it up and clean with intake/carb cleaner.
In doing some investigating into your rough idle, your ICV (Idle Control Valve) might also be shot. Apparently, this is under the air intake tubing right before the throttlebody. I'd check this first.
Like I said I'm not too familiar with the E23 7er's so my help to you is very limited, but I will do all that I can for you!