Tasma,

Back in April, I had the same exact question regarding my '82 240D. Check out the following link:

http://www.peachparts.com/shopforum/showthread.php?threadid=17047&highlight=throttle+plate

I did a litle research and found out that it is part of the EGR system. Since my EGR is no longer functional, I have decided that it is no longer needed but I haven't gotten around to removing it. I believe I can remove the plate only by removing the two screws that hold the plate on the shaft but, like I said, I haven't gotten around to it.

Out of curiosity, I disconnected the linkage that runs that throttle plate and ran the RPMS up to see if I could hear any changes to the RPM. I didn't hear any changes, but I'm like you, why would I have a plate restricting the airflow into the engine when it isn't necessary.

Herb
'82 240D
117,000 miles