Let me try and give a nice honest answer without bashing anyone.
*Steps on soap box*

Alright,
Different manufacturers have used the tornado in the past, and the concept used by Honda in its early days. Honda used the design first if I remember correctly. What they did was take two intake valves and one exhaust valve. No biggy, they do that today on some vehicles. What they did was offset the second intake valve a little from the first. When the fuel air mixture entered the chamber, the second smaller valve created a 'sort' of vortex, enough to turn a laminar flow into a turbulent one, therefore making the mixture a little better causing a more complete combustion.
The second use that comes to mind was used on the Crossfire injection on the early 80s Corvettes, Camaros, and Trans Ams. What GM did was to put a "Tornado" device under each of the two throttle bodies, mixing the air/fuel mixture a little better (once again turning laminar flow into turbulent) to prevent fuel puddleing in the intake manifold. Some of the Corvette guys that have the Crossfire have removed them or modified them because, yes, they are a restriction and they can live with the piddling problem. The addition of this only added to the efficiency of the car idling.
Now I'm not condemning or condoning the use of this product, just merely stating facts. One thing that you will notice about both of these applications is that they took place when the fuel had already been mixed with the air. Does that make a difference? I'm not sure.

In my opinion, the Tornado is a device that works on theory. Theoretically it should work, but does it in the real world? Theoretically I should be able to make a cat levitate. If a cat always lands on it's feet and buttered bread always lands butter side down, I could tie a buttered piece of bread to a cats back and make the cat levitate. Will it work, probably not, but it's a fun idea.
In my opinion, if it added to the efficiency of the car, the manufacturers probably would have put it on there in the first place. It's your money, you earned it. If you buy it, you can prove us wrong or right. If it doesn't work, you can always sell it off to another person or you can send it back. It will probably cost you $4 to ship it back, plus the 5% restocking fee. That's about $9 to try it. That's how I found a sub I like from Crutchfield. It's your opinion that matters to you. No one else’s should.
*Steps off soap box*

Let the bashing begin once again.