@njuguste; Where is it attached in the engine? Which Association of Engineers/Car manufacturer has endorsed it?
These types of gadgets are a complete waste of money. In the end, it pays to listen to what your parents told you when it comes to things being too good to be true: They probably are.
Do your research and trust your gut. Car manufacturers spend billions of dollars each year trying to come up with the next fuel-saving technology, so chances are if you haven't seen it in the showroom, then it is crap.
The rich have money working for them; the poor and the middle class are going to work for money.