no oil pressure

Just read this thread and now am wondering about my oil pressure and the FRAM filter I'm using. I've always used FRAM.

My oil pressure is good at start-up 60-65lbs, but when it gets hot, it'll drop to 8-10lbs at idle.
Motor is fresh 318 with standard pump but the 3/8" passages in the pump and block have been opened up to 1/2" for oiling mods.

Oil is conventional Valvoline 10/30 with Rislone zince additive.
Other contributors may be the cheap Equus oil pressure gauge.

The pressure immediately goes up when you touch the thottle:

1000rpm 15-20lbs
2000rpm 28-30lbs
3000rpm 40lbs

So that seems normal to me, so not sure. I'm not getting any noises or anything so maybe it could be the opened up passages??

Thinking of going to the VR1 20/50.