VXOC Astra-J/GTC

So my friend cooked his gtc 1.6 turbo and ive just stripped it got head skimmed and rebuilt with new gaskets.

The engine starts but soon after it starts to run a bit lumpy. I can rev is but hear a slight miss.

Now i am not sure why this air hole is in the rocker cover but i can clearly hear it sucking air in. And if i put my finger over it it sucks it in.
Can u tell me if this is normal please?.

I have included a picture of the vent and a video for reference. If u have any clues as to maybe i have some one way valve blocked from the mayo deposits from the hgf maybe?
I am not sure if the air and rough idle are related but any help is appreciated.
Ideas please. Thanks. T

Video link to onedrive..
https://1drv.ms/v/s!ApJp1ozW22j-xB-5GuwVxfvOLhfT

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Small addition to above. So if i remove the oil filler or the dipstick they both are under vacumn? Seems something is blocked i assume to create this vacumn. I am assuming the head is sealed or it would be blowing out not in. I cant see any water drop or further oil mixing with water but it is early days.

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So i have removed the crankcase breather pipe. It is sucking like mad for some reason. If i remove it its sucking more air down this pipe than the air intake lol. Is there a one way valve like a pcv? I have read its meant to have a slight suck to remove gases and stop positive pressure spreading the gases out the filler cap or shooting the dipstick out but this is really strong.

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Pretty sure the PCV valve inside the valve cover has gone.

Dont think the pcv in the cover has gone as its sucking through that hole fine. Ive seen it were this is blocked and its ends up with so much negative pressure u cant remove the oil cap lol. Could someone please check on their car and tell me what is normal noise or suction. Thanks

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It looks like negative pressure is expected and ok. Slight misfire so checkin it now. Exhaust still has loads of water in it so will try to clear it first.

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There should be 0 suction if the pcv valve is intact. Here's a video.. older engine but same symptoms https://www.youtube.com/watch?v=-YT1slY2Nac This would also explain rough running.

Thanks she is sorted now. Pcv is clear and suction can be heard through it which prevents the build up seen in the video where they cant even take the cap off. If the pcv blocks like theres was the suction is way too much. My engine is running fine now i got it up to temp once. The cat and exhaust where still full of water from previous HGF. Thanks for videos, it helps show there should be negative pressure just not a crazy amount lol. Tnx.

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