360 intake manifold interior holes

Like Rumble says.
The passages dead-end at the plate.
You can plug the holes but on a streeter, I wonder if it's worth it. I imagine they might cause some turbulence, but when and where, and how much, who knows. I have seen lots of 2bbl engines run perfectly well with the plate and open holes.

BTW, I got to know the part that screws in,In this case the missing part, as a floorjet; guess why,lol.
I recently had a vehicle come in that several other mechanics hadn't been able to tune. It was a 360 with a Holley 2bbl on it. I determined the carb was faulty and so took it off; and there was the hole with the missing floorjet! Oh-oh, I said; I wonder where it is? It's too big to get past the intake valve I thought to myself, but I better call the customer. Well the engine was a recent transplant, and he knew chit, so I had to go look for it right? I had to. So off came the intake, and it was nowhere to be found. Thank goodness, but I had to charge him for the extra time. I hate stuff like that. So I plugged the hole so the next guy to work on it wouldn't have to go through that again.
Then I modded the carb and the D and voila, very happy camper.