My 2005 People 50 came to me with an aftermarket fuel pump that I've confirmed as bad. That pump has only 3 fittings -- Vac, Fuel In, Fuel Out. I'm replacing with the OEM Kymco pump/filter combo. That unit has 4 fittings. As best I can tell, the 4th is a vent of some sort. Do I need to connect that to something? I don't see a stray line left around unconnected from previous owner's install of aftermarket pump. What's that venting, anyway?