normally i'd say stay well away, however it does seem to just be a resistor that bypasses the air temp sensor, permanantly telling the ECU that the air is cold. i might get the 20x lot and if it works you guys can have one (if you want and if you pay for pnp)
It says in the description that it makes the car run rich all the time, by fooling ECU into thinkin the air is cold. So that leads to far too much fuel being input into the chambers resulting in black smoke from the exhuast.
An engine works based on the correct air / fuel ratio for any given rev, it won't be efficient if too much fuel is being chucked in for not enough air. You will not see an significant increase in performance, only a sharp drop in economy. It is a total con and not worth wasting your time with.