Sorry, I guess I misread your post. Hard starting is characteristic of vapor lock, but if it was running and the stalled or "died", it is not due to vapor lock, which occurs under high temp, low pressure conditions. Best diagnostic step is get the engine scoped and hooked up to computer to see if you can get any fault codes. Other possibilities are the fuel distributor, fuel pressure(yes it can be off even with new pumps), intermittent on the injection control relay.

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Jeff L
1987 300e
1989 300e
1987 BMW 325