81 cb750c carb ?

I just went through the carbs on my 81 cb 750 and I can not figure out where a hose goes/does.  It is in between carbs 2 and 3 on a T fitting  above the throttle shafts. Its not the fuel intake because that is inbetween carbs 3 and 4.  What is it for?  Does anybody have a clue?  I can try to post a picture if need be but I'm sure you guys know what it is!  Thanks!