I've often wondered about that as well. If you look at a Weber manifold as compared to a 4 bbl. manifold, there is almost nothing to it. It's more of a mounting point for the carbs rather than a manifold. Just a straight shot from the carb butterflies an inch or two straight down right into the intake port of the head. It would appear that there isn't much opportunity to tweak the thing to get much of a performance enhancement out of it compared to the other Weber manifolds on the market. There is no plenum and no runners to speak of. Is there really a difference in performance of these various Weber manifolds?
