The idee is that the vacuum the fuel that the carb gives to much when closing the handle. When opening the fuel is a little bit slower then the air. The boost bottle returns the collected fuel (when clossing the handle) in the air when you open you handle.
The idee is fine, but when you have an excellent set-up of the carb, it won't gave any positive effect.
I also think that the malossi boxes gave more effect than the hard case boxes like the one from doppler, tnt etc. Because the volume is flexible.