What is the electrical component on Turbo inlet ...

[dcarlson12]

99 S80-T6 approx. 130,000 miles
Had the PVC system serviced last August after I had oil puke out of the dipstick pipe into the engine compartment.
Yesterday it happened again when I punched the accelerator and it shifted down one or two gears on the freeway.
There does appear to be vacuum at the dipstick pipe when I put a piece of plastic bag over it. I also placed a plastic bag over the dipstick and pipe and revved the engine but no oil puked out.
I have made an appointment with the dealer who did the PVC service but it sounds like he just wants to confirm that the PVC has vacuum which I am sure it has, at least under most conditions.
I am trying to figure out exactly how the PVC system works.
There is an electrical valve or sensor at the Tee where the PVC pipe connects to the Turbo inlet pipe on top of the engine.
I tried to find the name/part number of this 'valve' in the VADIS but it is shown only as part of Item 9 and sandwiched between the covers Items 20 and 21 of the attached file.
I am wondering if this valve is supposed to be open/energized at all times or just when the turbos kick in during down shifts of the transmission or ????
I asked the service manager at the dealership but he said he did not know.
The engine starts and runs fine and the CEL is NOT on so I don't believe there is any problem with compression on any of the cylinders but I have not checked them with a compression test....

[jimmy57]

heater so the moist crankcase vapors do not freeze in the line at the point they meet the air inlet which could be way below freezing in temps outside way below freezing.

[dcarlson12]

I guess a compression test is in order or would a leak down test be the best way to proceed?

[jimmy57]

leakdown is best.