Dave, The small amount of h2 used isn't detected by the vehicles sensors and being a small amount there's plenty of O2 in the air drawn by the intake for combustion.Most the the gasoline we use believe or not goes right out the tailpipe never being burnt(hydrocarbons and emissions) and the h2 helps burn this residual gasoline more efficiently before it leaves the combustion chamber,the same as hydroxy gas does to aid in better mileage gains.But with hydroxy the additional O2 IS detected by the vehicles O2sensors thus telling the ECM the motor has too much O2 which the result is the ECM increasing the fuel flow to the motor.This is reason for installing EFIES on the O2 sensors to counter this increased fuel flow thus allowing for better mileage gains.
Fatman 1, The fuel saver forum has a sub-forum created by the moderators just for the people experimenting with H2 only systems and generator construction if you want to learn more about it.Here's the link and you might consider joining they're a pretty good bunch over there.
http://www.fuel-saver.org/index.php