Here's a thought to back my opinion...
It's like putting a fan in your window, gluing the blades to each side of the window, and saying it's cooler in the room.
The "vortex" that it creates does not last. The "twisting" air WILL NOT swirl all the way into your cylinders. Though the idea is based on water and it shows it works well, the effect is not the same inside a car. Water is far denser than air allowing it's momentum to carry much farther.
People go and get it, spend an hour installing it into their car, and since the whole device is biased on saving gasoline, people are going to be driving more efficiently; not slamming the gas off of every light, etc. I think the thing has a "placebo effect". If someone spends 80 bucks on this, of course they are going to say it works no matter what....People want their purchases to work out.
[Edited 2003-06-27 03:51:22]