It increases power by decreasing vehicle weight by the ounces of a few bills, while decreasing seat padding and giving you a tiny bit more feeling of the power of your car. If you've watched the infomercial, the blond headed bimbo from Hawaii, is the intelligence level of the prospective customer they are looking for.
Checkout last month's or this month's Popular Mechanics. None of the "fuel savers", especially the Tornado, work--some were found to be even dangerous! They did mileage and horsepower on the dyno, with and without the product.