That's good to know Mike - I do have ARP studs.the head will come off in the car.
I probably will not swap on a turbo- I honestly can't imagine that much oil can pass through a .025" restrictor., Rather I'll just pull the engine.
Had a discussion with my machine shop guy today and he concurs with gas-washed rings being the probable cause. There's no blowby and no oil in the turbo compressor. He's offered to take the assembled long block and help me test/ tear down to find the problem.