Carburetor scoops do they make a difference?

I do not drag race, I road race and a daily driver in good weather. On the street and the road course my set up is mostly for cold air, but it does have some ram air effect, just not enough to be a big factor. I noticed a BIG difference in drive ability and seat of the pants performance improvements as soon as I did the cowl induction. Smoother running, especially in city traffic with the a/c on.

Do you get any gas fumes going into the cabin though with that setup? I'd imagine it would be pretty bad as soon as you shut off the engine...