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