Crankase vapour recirculation on turbo engines. Theory and how to test the valves. (Opel A16XNT)

The 2 valves downstream from PCV valve on a turbo engine Opel A16XNT. How they work and how to test.
How the crankcase vapours recirculation works in turbo engines. After the PCV valve there are other 2 important valves to know and to test.

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