The smoke part of your symptoms indicates that you have more than the idle stabilization (dampening)problem that has been talked about recently.

Our approach for your car would be to verify pump timing (we use a light that makes this as easy as a gas motor - measuring that is) and then pull the injectors for bench testing and check the compression before they go back in. With the injectors out the prechamber balls acn be inspected. In all 2-3 hours work.

If all of this is good you should take the pump out and send to a Bosch Diesel Service Center see:
http://www.boschservice.com/

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician