What is your idle speed? On mine there is a sticker that has the min and max idle speed. An engine with some wear on it may need a little more then max idle speed.
re-adjust idle speed and damper. Back out the damper till it has no effect on the idle. Adjust the idle speed. Then slowly turn in the damper screw. The goal is to remove as much shaking as possible with out raising the idle speed.
When I replace my Rack Damper/Governor Idle Pin the old one had a worn tip on it and the spring tension seemed to be about 1/2 as much.

Does your issue only show up after the Engine is up to temp and running say after 15 minutes?

What type of driving do you do. Mine drones around town and seldom gets on the Freeway.

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84 300D, 82 Volvo 244Gl Diesel