I'm assuming by the picture you posted from the N54 tech PDF that the check valve would be located near the top right corner of valve cover in that picture.
Here is another picture I found and on ALLDATA for 1 it says
Detach crankcase breather (1) at cylinder head cover.
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So the lower line is a breather also? I thought the bigger fitting just above 1 was the PCV line.
EDIT: looking at this new picture the PCV block seems to sit directly ontop of the valve cover hence why we would not see it in my first picture. But if you look at the first picture on the inside of the valve cover you can see two square holes and that is probably where the PCV block sits.