I'm interested in how this would affect the combustion process and how much
oxygen/hydrogen would you need to make a difference.

At 3500 rpm our engine, with displacement rounded to 2 liters, pumps 7000
liters of air per minute.  How much hydrogen would the gizmo add per each
combustion cycle?  That's fairly easily calculated once you know output of
the gizmo.  Keep in mind half of the produced H+O goes out the tail pipe as
our 4-strokes fire every other revolution of the crank.  Maybe we need
direct H+O injection?

Aw.. somebody do it just for fun of it and I promise I'll build those belly
pans I talked about!

Chris.