The fuel rail supply side issue may be a red herring as from running at 28000 kpa to key off the rail pressure drops down to 650-850 kpa within approximately 4-5 seconds and there it stays.

During the times that it does start this KOEO pressure is the same as it is when it refuses to start. Also it has now stopped starting on a direct fuel feed and will only go on a sniff (unless you crank within 10-15 seconds of being switched off)

Also a new code has logged which was never present with the original pump

P0089 fuel pressure control valve
circuit low
intermittent