That vacuum line coming from the fuel regulator is not a vacuum line per se. That line goes to the hose that extends from the valve cover gasket to the air cleaner.
The purpose of that tube is to overflow fuel to the air intake in case the regulator diaphragm goes faulty. (Fire preventative.)

I don't know if sucking on that tube would have been such a good idea.

If the diaphragm has had it you need a new regulator. (New one $$$)