Float chamber balance and vent pipe

This pipe appears to connect the two air cleaners (which in turn have vents to the float chambers) and also to the radiator area.

Obviously an engineer would have reluctantly added it to the clutter for some reason, but what?

Guessing emissions. Can’t vent fuel vapor to the atmosphere. This way it gets drawn back in to engine. And showing the carbs the same atmospheric pressure without airstream interference is desirable