Vent tube question 68 Barracuda

We need a bit more info.

When you are filling up, tell us about the fuel filler handle on the gas station (better yet a photo)

Question 1) should air flow through the tube when I blow compressed air through it?
Yes

Question 2) Is there a check valve of some sort in the end?
No


Question 3? what would happen if I cut off the end so the opening is the size of the tube?
The flare is there to keep the short hose from the fuel filler neck to the vet tube from slipping off.

Your filler neck should look like this
Screenshot_20210411-081000.png

Just inside your filler neck on the top of it there is a piece of metal welded in that creates the vent line to the tube. This is the end inside the gas tank, fuel goes in on one side and air goes out on the other. This tube end is rotated 90 deg in the photoScreenshot_20210411-081830.png