Mercedes Benz repair: 1980 300sd, mercedes benz 300sd, vacuum gauge

Question
hello, i have a 1980 300SD with 338,000 miles.  A quick two part question;

one,
when i shut it off the motor keeps running. I think its the vacuum shut off, can you confirm?  as well i cannot find this part on any parts lists.  what, exactly, am i looking for to replace/repair this problem?

two,
she runs fine in town, but after 20plus miles over 60mph she rocks and shakes something fierce when im stopped.  why does my mercedes physically move so much after running it hard?

Thank you very much for your time on this...

Kuper

Answer
Engine Rocking:
Rack dampener pin bad?
Plugged fuel filters?
Plugged fuel tank vent?
Plugged fuel tank strainer?
Fouled injectors?
Bad engine mounts and engine shocks?
Primer Pump leaking = sucking air?
Fuel line leak  = sucking air?
Diesel Prechamber fouled?
Valves out of adjustment?


Start car, attach a vacuum gauge in place of shutoff valve, turn off engine, if it shows thirteen or better vacuum, the shutoff valve is bad, but if it has six or less = a bad vacuum leak or failed vacuum pump or pump check valve.

PART NUMBER SEARCH RESULTS WITH PRICES
Vehicle 1980 Mercedes Benz 300SD
Part: Shut-Off Valve
 Note:  At Injection Pump
Pulls injection pump rack to stop. Requires (2) 001 074 20 80 gaskets.     
D2020-11537 Shut-Off Valve IN STOCK $66.02  
  
PART NUMBER SEARCH RESULTS WITH PRICES
Vehicle 1980 Mercedes Benz 300SD
Part: Vacuum Pump Check Valve
 Note:  
 Engine: 014182-
D3012-25391 Vacuum Pump Check Valve IN STOCK $37.73  

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