The "port to nowhere" is where the red silicone vacuum hose connected which supplied filtered make-up air for the tube which passes through the exhaust manifold and then through the metal tube, covered with a white insulating sleeve, which connects to the choke housing. The carburetor's internal vacuum leak, as designed, pulls heated air to the choke housing, thereby exposing the bimetallic spring to heated air, allowing the spring to do its thing and open the choke as the engine comes to operating temperature.