breather pipe

On investigating a newly acquired 1995 Thunderbird I have found a pipe running from a connection between carbs 2 and 3 to the breather connection on the rear of the fuel tank. According to my Haynes manual the tank breather should go to some sort of valve to prevent leakage if the bike inverts. No sign of this. I think the carb connection is a tee connection between the top of the body and is either a vacuum or some sort of breather, Haynes is not clear where this should go. Help would be appreciated.