What is this?

[Ultrasummer]

So I was looking at my carb this morning. Recently I've been curious about changing over to a Holley 2 barrel carb. Currently I have (or my best guess) a Rochester 2G. 1968 C10 with a 307 and manual 4 speed. Seems to be "mostly" original. Anyways, it's been hesitating here and there, on starts and stops. Considered a clean up and rebuild for the carb. Browsed replacing it with a new one just because. Basically considering all options. So upon taking a closer look at what I have, I notice on the back of the carb, there is a rubber hose, maybe 2 inches long, with something capping the end. I'm guessing this is some kind of vacuum line but where was it supposed to go? Is it that my simple little 307 isn't equipped for that kind of vacuum line? Is this the reason for when the vehicle hesitates?