The one on my 74 Duster was crap rotted. I ran the thing off the sender, up through the trunk, into the top or rear 1/4, then back into a bung I drilled into the filler. Works like a charm. In other words, I duplicated the older style
If you hooked up one end of the tube to the sender extra port, and to the filler neck port you do not have a vent. Either you have a vented gas cap or there is another opening in the tank somewhere.