Hi volume oil pump
It's been a while since I have driven it, I took it off the road and haven't put insurance back on it.
If I recall the PSI did climb with engine RPM, usually staying with the 10 psi/1000rpm rule.
The pressure on a cold motor is way up there If I recall it was 60-70 psi when the engine is cold.
Thanks a lot guys for all the info, its a weird problem for sure.
Brambles