Carter AFB

So it is a performance carb not a production carb

My bet is if there is a vacuum operated piston inside the choke housing, it is either supplied vacuum from internal passages or through that port from an external source.

Some testing will tell if it needs to be capped, supplied a vacume source or left alone.

With everything hooked up as is, is there vacuum at the port at idle or at rpm (2000?)

If no vacuum then it does not need to be capped.

Next remove the electronic choke (note it's position)

Look inside the housing, with a vacume pump hooked up to the port, slowly apply a vacuum. Are any parts inside the housing moving? Can you hold a vacuum?

Report your findings