The only port that bypasses the filter I'm aware of goes to the HPOP reservoir. There is a valve that should shut it off once the pressure builds in the main oil galley. Even if there was a problem there it shouldn't cause no oil pressure.
Someone had a problem awhile back where there was some sort of bleed on the timing cover above the pump that had come out. Since you replaced the cover I wouldn't think thats the problem.
Haven't had one of these apart far enough to give you a good place to look.
My suggestion (what I would do) is drop the pan, then with air pressurize the system through the port on the side of the rear cooler header. Then look for severe leaks