'T' connector pipe that goes into the valve in front of the engine head cover is the vacuum line to actuate on the air injection system(at idle it'll be closed - depression isn't enough to open the circuit- at throttle it'll be open and will inject air to the exhaust chamber). Its about emissions, though I believe it cools down exhaust valves a bit. The other connection on the carbs might be related to emissions also -cannister circuit perhaps - My bike is european and doesn't have it...