progress and question

well i got my flowtech shorties installed and the trick kit for my holley 600 and i hope to have it running by wed/thur, but i need some help with my fuel pressure regulator, its a mallory 4309, and the thing has 4 places for connections, i have one coming from the tank, one going to the tank, and one going to the carb, so whats the other one for

ill get around to posting some pics later tonight

http://img54.exs.cx/img54/2810/picture0019zo.jpg

http://img54.exs.cx/img54/1343/picture0025np.jpg

http://img54.exs.cx/img54/9453/picture0035bv.jpg

http://img54.exs.cx/img54/657/picture0045xi.jpg

http://img54.exs.cx/img54/4740/picture0052kw.jpg

http://img54.exs.cx/img54/5076/picture0069xi.jpg

and the fuel pressure regulator

http://img54.exs.cx/img54/4328/picture0084ie.jpg