This seems like a worthwhile enough topic that I want to break it out as a separate thread.

My ‘73 1.7 FI car currently has these lines open, and I’m not sure if that will impact how the engine runs.

Obviously everything ultimately should be connected but I’m not sure if it’s critical to the engine running properly or not.

EDIT - wrong picture, sorry.

You shouldn’t have anything open to the atmosphere, dirt particles can enter past the air cleaner.
I’m not sure what you are pointing to?
You can remove the deaccl valve and cap all three vacuum connections.
Capping will change the idle mixture as air is bypassing the throttle body.

Posted the wrong picture, sorry.

This is what is open.

Click to view attachment

That's the spark arrestor for the crank case ventilation. There should be a hose running from the bottom ports to each cylinder head and the top port connected to the port on the oil filler. Not critical and I think there is debate about whether it is good, but disconnected means you could have an open port on each head puking oil and an open port on the filler sucking dirt without having it hooked up or some alternative arrangement.

Thanks Brock, very helpful for a Type 4 newbie. I’ll connect it all up but good to be able to mentally separate it from the engine running issues.