Answers to previous questions:
Yes,3 different oil pressure guages, the standard nissan sender unit, autometer pro comp(brand new) and ABW oil pressure sensor, all read 92 psi as already putlined.
Yes the oil filter has been checked and changed and appears not to be causing a change in oil pressure, 2 different brands have been tried with no change.
Engine oil temperature is as per factory specifications, running motul
8100.
No there is not an excessive amount of oil in the breather system or rocker covers, the engine is fitted with both a tomei head restrictor and 1.2 mm restrictors for the turbo chargers, these are both normal upgrades which i have done on many other rb engines and no problems arissing from them.
Yes turbo charger oil supply is fine.
Still at a loss but head is being re serviced at the moment as valve guides and valves need re doing so still awaiting its return before i can really look any further into the problem.