I agree with what the others said concerning an Air leak. I had that same problem but not as bad. It turned out my Fuel Inlet Hoses were hard and while the clamps were tite you could still rotate the Plastic Filter.

For some reason it only let Air in when it was hot under the hood. Some SAE 5/16 30R7 Fuel hose that ever Auto Parts store sells (also rated for Diesel) took care of the problem for a few dollars.
But, also look under your Fuel Tank and see if the Hoses there are seeping Fuel. If so they need to be replaced also.

Also, is your Idle speed within spec.

I believe the Rack Damper was put there to take care of the extra shake when the Car was New and all the Engine components were in good shape. It was not intended to compensate for the Engine not running correctly or other problems like the Motor Mounts.

And, in fact I had to fix a list of stuff before the new Gold Color Rack Damper Bolt I had bought had and helpful effect.

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84 300D, 82 Volvo 244Gl Diesel