Okay, so at the end of my session of hpde a couple weeks ago, I suddenly lost boost pressure. Looking for a good order of troubleshooting. The threads on nasioc all seem to jump around with a bunch of self proclaimed experts, so hoping to keep things a little more step by step here.

I'm not building any boost, it's not simply leaking by as a result of loose intercooler hoses or similar (I've had that on a previous wrx, and it is a very tell tale sound)

Peaking at about -0.2 psi, so essentially nothing. The eclip on the wastegate arm appears to be in place. The wastegate is opening and closing with a strong grip and a good pull. The hoses back to the intake appear to be in place and no obvious leaks. Went ahead and reset the ecu using the accessport, but no change.

At this point, my mind is going to oil build up in the turbo/intake (or oil starvation, I suppose) followed by "pop" so to speak during the high g force cornering, meaning I need to swap out the turbo.

The question, then, is: are there any more diagnostics I should do first before I start pulling things apart?

I have a spare turbo, but no idea if it is any good.