Shuuuu,
So here goes, built motor, everything pretty much new, however re-used the OEM NEO oil pump, which similar to a GT-R N1 pump.
With the pump, modified it and installed a set of Spool Import Billet Oil Pump gears and installed the matching collar to suit from Spool as well.
It provides good oil pressure, cold start up about 4 bar on idle (according to my Haltech pressure sensor & the dash shows about the same too)
Oil pressure increase as RPM increases and appears the pressure relief valve works corectly too and plateaus about 8~9bar with higher RPM.
Once warm, I get about 1.8bar of oil pressure on idle with Penrite 10/tenths 15W50.
Car is running a JHH oil relocation block, -10AN lines to a GREX relocation block and into a 25 Row Setrab oil cooler with a Z422 Oil Filter (has anti-drain back)
Now the problem, it takes a good 15 seconds to build oil pressure when you 1st start the car when cold OR when it has been sitting for more than 10 minutes
I've changed the oil filter just to be safe, still same thing.
Lastly, this has only started to happen after the skid pan day... If I did crack the gears, the car would simply just stop building oil pressure but it's still making pressure.
So this has lead to think maybe the oil pump housing itself is damaged?