I would bet you a doughnut if you run a much larger tube from airbox to back of carb you will pick up power. For instance on a cr 85 powered quad going from pod on the back of the carb, I had to use a tapered silicone boot to run the same pod filter I used to run on my hybrid. After I didn't have to jet the bike down and loose power unlike all the other smaller tube size stuff I used, now on a Hybrid a couple jets is only a couple percent hp loss, on the cr85 it was magnified so 3 jets was like being down 6 hp.   

The cfm measure you need is instant and turbulent, not constant and steady hence a larger diameter to overcome the restriction on the walls.