1986 yamaha 150 prov componet question

[mikestarkey]

on my 1986 prov 150 i have a box on the right side of motor with an orange lever on top that you can turn either direction. left side of carbs hose run to it and hose from air in take goes to it, should both sides of carbs hook up to it or not. also what is this piece of componet called on my motor. new to this motor and just asking. also is there a certain setting that this should be set at. thanks mike

[boats.net]

Don't recall seing anything like that on a ProV 150.