No oil pressure at idle

Recently fixed the wiring to my oil pressure switch and was dismayed to find the oil light glowing at idle. I removed the switch and placed a mechanical gauge, and it confirmed. Basically zero oil pressure at idle. Comes up to about 5psi at 1500, and climbs from there. Snapping the throttle got me 40-50 psi.
I changed the oil/filter and it made no difference. (No glitter came out either).

Engine is a overhauled Magnum 360. I hadn't noticed any engine noises that would lead me to believe it had oiling issues. Main and rod bearings replaced and plasti-gauged within specs. Cam bearings were not touched when the lunati roller cam was installed. Oil pump is stock Magnum, I just took it apart to check for scoring on the rotor (looked ok). Summit oil pan and pickup (I didn't use Teflon tape on the pickup threads, was I supposed to?). Stock magnum oil pump drive. Wix 51515 (tall filter) and 10w-30 oil.

Anything I can check before I have to pull the motor?