Mounts are good and relatively new. I got the car 3 yrs ago? Replaced air cleaner bracket, noise was bothering me. Also tried adjusting the damper bolt. Easier than I thought it would be, fyi cut your 12mm crap wrench in half to make it much easier.
Result, no effect on the idle turning the bolt. Hmmm, i think we may have a winner. New one was ordered last night just in case.
On the "you've got to be kidding me" side, after a start up and test ... the car didn't shut off with the key. Great. First time that's happened with this one. My 81 had that and a valve adjustment made that go away.

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1982 300CD (daily driver) 186K clicks