Three little piggies carb nipple version

I have an '81 kz750H ltd. I am sure this has been answered a thousand times before, but I can't find it in the Clymer or on the site. Anyhoo, from the vacuum switch there are two lines to two suction valves and also a main line to the air box. In addition, there is a smaller diameter tube that T's at the carbs. I know these tubes go to the vacuum nipples on the carbs, but does it matter to which they go? I don't think it should, but regardless, that only eliminates two of four carb nips and leaves one for the vacuum nip on the petcock (does it matter to what nip this one goes?) So if the petcock vacuum line takes up another carb nip, what about the fourth??
Anyway, help would be great.

The fourth port should be capped. The diagrams at Kawasaki.com are often times helpful. It doesn't matter where they're connected, but the air injection system tubing is normally on the #1  carburetors. #2 has the petcock vacuum line & #3 is capped.