Dom, is your scoop sealed, if so you wont see a vacumn
in the scoop area, specially on top end, that area will
be under a slight pressure, about 5"-8" of water at
your speed. The loop tube is for a hard leaving car,
when you launch the fuel sloshes up and out of the vent
falling into the carb causing the carb to go dog rich
EDIT
also a set up that didnt have a air cleaner and
usually no hood, the air passing over the carb would
suck fuel out of the vents and spray on the windshield