inspection question?

Hey, I have a 76 1/2 ton 4x4 chevy pickup, have few questions for inspection. Unlike my other chevy trucks, this one was checked for a vapor canister, and did not have one so I found one and hooked the plugged off line into it. This line seems to be plugged in alot of trucks between 73 and 80 (canister is gone but line is right there with a little white plug?). But the guy at the dmv(our inspection lanes in delaware) tells me that the other line going to the carb needs to be hooked up? I have an after market carb and dont have any where for it to go. Where is it supposed to go? And it failed the tank pressure test and as far as I can figure if I check the tank, the line going to the canister, and the line going to the fuel pump to the carb and everything looks fine what else could it be? Thanks for any help James