Here is something I came across the other day:
The Tornado device, often seen on late-nite TV infomercials, is a cookie-cutter shaped piece of metal that slides in your intake and supposedly creates a swirling motion in the incoming air. The manufacturer claims that this swirling motion increases fuel economy and horsepower.
However, this device is a waste of money and really just restricts air coming through your intake. Actual dyno tests made after installation have shown either no difference or a small loss in horsepower. The air cannot continue its swirling effect all the way through the throttle body and intake manifold, thus renderring the Tornado device useless. Our intake systems are already designed for maximum airflow, and putting fins in the path of the air only blocks that flow. In addition, the valve setup of our engines (2 intake, 1 exhaust) already mixes the fuel and air well enough to negate the need for the Tornado. Buyer Beware.