Because it seems to have pressure even on a hot start, I am also in the drain back issue camp. I wouldn't go crazy changing and adding things. Troubleshoot what you have first? Lots of smart/experienced people here. Listen to them ;~)
Wouldn't hurt to pressure test the oil pump feed galley (from pickup tube to pump). I believe I saw on the site somewhere where someone had opened up the galley and it ended up sucking air...
Update: tore everything apart, didn't find anything out of the ordinary. Changed rod bearings to .001 tighter clearance, re used mains, crank was fine. Added more drainback holes, and went to TA scavenger pump housing with external pickup, put it all back together, annnnnnnddd STILL had the same issue but wasn't nearly as bad. I called TA and spoke to Tim, as soon as I mentioned the crossover line he mentioned I should just cap that off, and they don't do it, ever. 5 minutes later I had it capped off, pressure was about 10 lbs higher across the board and doesn't drop off anymore. I had the same mod on my other engine, and never did it. No idea, but it fixed it and I'm not questioning anything lol. Thanks for all the replies and info and thoughts. Greatly appreciated. Posting my dyno vid/numbers up Tonight.
Yah get me thinking now why it made a difference. Im theorizing when the rear galleys (lifter) are looped (connected) it allows the right galley which feeds the mains, another huge area (left galley) to bleed pressure. Putting the allen plug back in isolates the right galley from the left and allows the right galley to build pressure easier, instead of the left galley trying to drain it (lifter bores)
Way back I had a buick engineer tell me to tie the galleys together to help drop oil pressure. I had high oil pressure. Never did the the suggestion as other problems had developed.