I understand the reasoning for the slope, and as ronin said in a perfect environment it would probably work. However it is hard to argue with facts, and I remember a while back reading some air pressure tests showing the front cylinders being starved for air. The theory of the slope is good but in practice it does not seem to work as well as expected. That being said, I can't remember seeing any similar tests done on aftermarket plenums.. I really need to dig up that post.