can I trouble you as to ask where that OVP is located? Thanks

Is the shutting off a gradual 'choking' or is it like you turn the key off and the car continues on a normal idle until it abruptly quits? If it's the choking then it's definitely vacuum related. If it quits abruptly then it still may be vacuum related, like a shutoff that sticks until it is overcome by vacuum which might take a few seconds. I had a vac leak inside the dash once, at a vac pod. Caused clunking when coming to a stop and gradual choking on shutoff. Make sure there are zero little vacuum leaks from cracked or disintegrating rubber connectors in the engine compartment first. Then check the vac shutoff on the back of the injection pump. You'll need a Mityvac tester for this. If the shutoff works on application of vacuum, it's not the problem.

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