Okay, here's my two cents worth...
About a year ago I read an article in Sport Compact Car magazine, where they tested the Tornado under controlled conditions (i.e. , dynamometer, etc.). They even had the guy from the infomercial witness the tests.
The results were as follows: the dynamometer showed no measureable increase (or decrease) in horsepower as a result of the installation of the Tornado. The infomercial guy refuted the results, saying that it was improperly installed. So they let him do the install for the next test.
Again, no measurable results. Basically, another snake oil product...it's sold in the same stores where they sell those magnets that you put around your fuel lines to improve fuel efficiency.
Besides, any air swirl tweaking must occur near the combustion chambers for any performance gain to be realized...besides, that swirl (allegedly created by the Tornado) would get dissipated with the variety of plumbing that the air must travel through before getting there. That's where head porting comes in...and MB already covers that pretty well.
The only airflow change that could give you a real measurable horsepower increase would be by cooling the air and compressing it...but someone has already invented the turbocharger/supercharger and intercooler.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car