I need a little enlightenment on this Holley carb

That may be the PCV hose from the PCV valve.... see if there is a plastic or metal cylindrical 'thing' stuck into the valve cover to which that hose attaches. But it could be the breather line..... a pix is needed.... upside down is OK LOL

See that oval shaped plate below the carb in the 1st pix with 2 bolts holding it on? That is the cap-off plate blocking off the EGR port on the manifold. (An EGR valve originally was bolted on there.) So the intake manifold at least is a '73 or '74 or later manifold.