due to my lack of understanding the english language, I can’t clearly identify which tubes you mean.
A pic would help.
Is it the common tube between the intake boots? Where the vacuum gauges are to be connected during service?
You may seal them individually or leave the common connection tube, up to you as long as they are sealed.
Is it connected to the carb housing ?
That is carb ventilation / overflow.
Diameter is small, but there shouldn’t be any issue in connecting them together with a T-piece and have single air intake/drain line.
The end(s) must be open!
Letting the air in is much easier than getting the fuel out of the bowls 😉
FOT and it’s fuel demand must be covered by the air intake.
Cheers, Michael (from Germany)