I know that a lot of the performance bikes have modified intakes that help with air going into the carb, and its not a scam at all. Its not a small little device you wedge in, but a redesigned intake system before the air filter that helps the flow of air.
These things typically cost a good chunk of money, and are mostly for performance bikes. Our bike I doubt sucks enough air even at full crank to be restricted by its stock system. The only thing that may help us, at speed, is a ram air system. Quite a bit more then a modified breather box, and a lot more expensive.
With the location of our box, under the tank, I doubt that there would be an easy solution for getting our breather box any better.