Sounds to me like it's pulling air into the injection pump. I would replace the 1/4" fuel supply lines from IP to filter and from Filter to car. I would also make sure all the banjo fittings are sealed with new crush washers. Also make sure fuel filter is sealed.
You can add a small inline electric pump pre-filter to pump the fuel if you think the injection pump shaft is pulling air. Check the tension on the injection pump belt, if it's not fairly slack then most likely you will have a bad input shaft bushing/seal.
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