The two connections on the air box are the temperature sensing part of this system - depending on the temperature in the air filter box, the vacuum (or suction) is allowed to flow from one hose to the other, go down to the air temperature control valve, and then open/shut it as needed. Since the two-nipple thing is basically just a vacuum switch, it doesn't matter which hose goes where as long as both are on a nipple.
One of the hoses has to end up on the intake manifold - which is the source of vacuum for the system, the other one goes to the flap at the lower part of the air filter box, then attaches to a nipple at air temperature control valve - that Neils upper picture above






