Oil pressure.

I have oil pressure problem.
when the engine is cold I have about 40-45 psi.
when it is hot it drops to less than 5 psi at idle, about 5 psi at 2000 rpm and
a it increases at higher rpm but not over 45 psi.

where am I loosing the pressure?
I know it can be the oil pump, but I have changed it, so thats ok and also a hv pump.
It can also be the main bearings and the connecting rod bearing ( at the crank end, can it be the other end?)
And it could be the camshaft bearings.

I have checked one main beraring an and one connecting rod bearing and I don`t think they look so bad that I should loose my oilpressure.

Can it be anything else? like in the cylinderheads?
If anyone knoes any places to look it would be nice to know 8)