I think soon we will have an answer to two questions.
1) Can we get rid of the sulfur smell coming from the muffler.
and
2) Will I ever be able to increase the gas milage and polute less.
Check out these websites form more details. Granted, these products are more beneficial for diesel engines but they are working on designs for gas engines.
At the same time that I post this I wonder if any of you has more info on these products.
www.chechfi.ca
HyPowerFuel
HydrogenBoost
And if you google hydrogen injection you'll find more websites.