I have a qustion about the fuel lines the car has the return the feed, what is the 3rd line the manual says its a vacum evaporator line, but were does it run, im not sure. By the way i have a 93 fd it that helps...

 

It is a purge line; it sends evaporated fuel gas to a charcoal canister that filters it. It is an emissions thing. I yanked mine out a long time ago with no negative repercussions.