No boost, leaktester won't hold pressure

[Leon 20VT4]

One morning my boost was gone. It won't get above 0Bar.

The leaktester won't hold pressure so there is a leak somewhere. I noticed that pressure is escaping out the pancake valve, valve shot? I forgot to remove the oil cap, is that a must?
Even if i block the pancake valve it still won't hold pressure. It sounds like i have leaks more than one place. Can't figure out where. Tried with soapy water and found some minor bubbles but not the source to the problem.

Is the spider hose supposed to be pressurized when i do the pressuretest? (The spider hose is rebuilt)

Any faultfinding tips? How can i narrow it down?

[MacDaddy]

I know on mine i couldn't find the "boost leak" because the PCV valve was leaking the pressure into my crankcase which would then force oil into my exhaust and make my car smoke for days.

turns out my boost leak was the PCV leaking boost into the crankcase and causing inconsistent performance.

[Leon 20VT4]

How exactly does this PCV valve work? Earlier when i have done leak tests there were no pressure escaping from the PCV valve. But then again isn't it weird that there are pressure in the spider hose? (PCV valve taken off and capped the y-pipe hole during leak tests)