All very good ideas. Diagnosis while sitting still with the air cleaner removed and a metal cap for the turbo air intake is a good plan. If you really are sucking oil into the cumbustion chamber (a very real possibility) you stand a good chance of a runaway. The only way to stop one is to close off the source of combustion air - be carefull, the spinning turbo vanes will eat your fingers. Check the simple stuff first. Has anyone looked at the oil pressure sending unit? A leaky OPSU can still give a pressure reading while dumping oil. How about the fittings for the oil cooler? The oil filter housing? And so on. Just because the car doesn't leave a puddle, doesn't mean it isn't leaking. Good luck!