its a scam piece... it doesnt work.
if you want to do something good with that 8 dollars, go buy a gift for toys for tots. youd get much more value and satisfaction from your money that way.
the idea "in theory" sounds decent, but the reality is most engines mix/burn air/fuel mixtures at a near 99% rate anyway. the other 1% is usually caused by heat (or a horrible tune, which this would not solve).
just because it "fits" where they tell you to put it doesnt mean it works. Id even go as far as to say all that device does is impede incoming air.