Valves being open will have nothing to do with what he is seeing. The air is getting from the turbo to the engine as was stated above through one of the oil lines. Apparently this is somewhat normal as I have the same thing on my 35r. I'm not sure how much is normal, but I have 75K miles on my turbo and it just started to drop a good 5psi from 7400-8000 rpm. No other boost leaks in my car as I have tested the rest of the system without the turbo and it holds solid.

 

Cap off the throttle body not the UICP.

 

What would that accomplish? Keeping dust out of the engine? He is pressurizing the system from the turbo to the upper IC pipe. He would get the same results if he capped off the turbo outlet.

 

this is normal for garrett bb turbos. i was told by tech at garrett that once the turbo is spinning with oil going over the bearings it seals.