Can vortec air intake type devices improve gas mileage?

this is another of the "mouse milk" devices sold to increase the mileage or performance of your vehicle.  the vortex type products will induce some spin to the incoming air.  however, the incoming air is violently redirected , and bounced around in the intake manifold as the intake valves open and close.  any spin induced before the throttle body is of no value.  in fact the vortex product only restricts the incoming air.  there have been several field test of most of the aftermarket devices claiming to increase mileage. Most devices have proven to be of no significant improvement, but decrease mileage and performance.  you can add a turbo-charger or super-charger to improve performance.  with the government pressure on the auto manufacturers to increase their fleet mileage figures, they would certainly incorporate any of these devices if they work. most people who buy these things want the to work but they don't.