Update!

After about 1000 miles from the initial installation of Tornado Air now I got 391 miles per 21.2 gallon fillup. This is 18.44 mpg. This is great. It looks like the benfit of the swirl air inside combustion chamber outweighs the air restriction it adds at the intake.

The idea is similar to GM's vortex engine



Search for swirl in auto golssary

swirl - A cylinder-head design that causes the air/fuel mixture to enter the combustion chamber at a high rate of speed, increasing its atomization.

The new Nissan 350Z also has swirl control valve