If ya don't inject oxygen the O2 sensor doesn't detect more oxygen and richen the air/fuel ratio which ya want ta do the opposite. The HLNT unit injectes a very small amount of hydrogen and also the oxygen that poses the O2 sensor problem. A garage type hho builder mistake.
Are ya sure ya want to continue down this path and destroy the nonsense which you are tryin ta sell? I warned ya about goin down this road. You're not comin up aces here dude.