I believe the pieces you mention are part of a fork type assembly. They rot and fall off with age. Decreasing the full throttle range substantially. Just like little bushings that slide onto the forks to prevent noise

The best part though is they are really cheap if you can get a dealer to identify the part number. I had the part number earlier but it is lost for now.

My 83 240d has that set up but I never knew exactly how many years used it. I originally used a little creativity to substitute them but they are only about .50 cents each and you get the right wall thickness to eliminate all slop in the assembly.

Although that fork assembly could be considered a universal. I suspect the primary reason may have been to reduce noise transmission originally. Or some allowance for engine movement.

Maybe both for all I know. I though the remaining partial one in my case was made of rubber. It has been a long time though. One was totally missing and only a small portion of the other one remained.