I'm replacing the vacuum lines on my '74 2.0L. After removing the airbox to get a better look at the throttle body etc., I can see this hole (yellow arrow) that appears to be open to manifold (but maybe not) ... it looks wrong to me, but I am a rank amateur with 914s.

Advice most welcome.

It's the way it is made.

I believe there are two through post on the plenum. Probably for strengthening the plenum. They don't open to the inside. I'll have to check mine to see if that's where it's positioned.

Thanks guys .... I also did some more searching and found an almost identical question, with similar answers

Seems like it is the top of a strengthening post in the plenum.