Anybody ever tried this little gizmo?

The points of both the posts above are on the money - so to speak. The Holley 3310 for Chevy's 396 for example had snivies to balance booster distribution direction for that engine and intake.

As far as the percentage of charge, point is valid, but the mass quantity is different than the volumetric relationship. Stated another way, with the throttles near closed, there is low pressure (high vacuum) which aids the mixing of fuel droplets and direction of flow toward the valve that is opening. Some portion of fuel may even vaporize. As the throttle opens, the pressure difference is reduced. etc etc

I'd be more interested in experimenting with and understanding what BLP has come up with than the sheetmetal device.
My suspicion is that it may be useful for specific setups rather than a universal miracle product.