everyone needs to read what he said closely. I personally think that the chemical reactions look good on paper, but the biggest flaw is that the system is "real". You are not performing electrolysis in an isolated system and your car is not going to be efficient in extracting any "extra" energy from this reaction due to the fact that it is a COMBUSTION engine. A lot of energy gets lost as heat in a motor, and as Mitch just mentioned, your car would have to work harder to increase the energy supply for the reaction.
I think a more efficient method is to buy a hydrogen tank with a pressure regulator and hook up a line to your intake manifold....haha. I don't know that you would save enough on gas to offset the cost of the hydrogen tank though.