It is not a vacuum line, and it doesn't attach to anything. See this link...
http://49ccscoot.proboards.com/threa...ctions-diagram
As for a vac line diagram.....I have a photo of my setup. Vac hose runs from manifold to fuel pump, with one 'T' installed near the carb, for the air cut valve located on the right. Very plain to see in this photo.....