the more i hear about this device the more i'm becoming convinced that this is utter crap. buboy, no offense to you, and i certainly respect your opinion - but your friend mr. planas simply does not have any facts to back his claims up and any responsible consumer will demand reasonable proof that the device works as advertised before dropping a lot of hard-earned cash on it (with the possible exception of julian up above)
these 'swirl' devices that modify the intake charge have been around in different forms for years - the most ridiculous one i saw had a small electric fan actually "forcing" air into the intake through a tube...again, NONE of these devices have worked as advertised.
the only possible way i see this working is ghosthunter's theory of leaning out the fuel mixture - but (a) you can do that yourself if you knew how the ecu works (remember the days of carbureted cars when you had the "choke", or you could turn a screw and the engine would run differently? it's kinda like that)...and (b) it's not too smart - you'll have an engine continually short on power and prone to stalling.