Well, the statement that a normal intrnal engine is only 35% efficient (probably true) being followed by the analysis that the remainder of the fuel is unburned or partially burned is total hogwash.

Confusing burn efficiency with thermal efficiency is a huge howler.

I would imagine that if you fed extra hydrogen (and oxgen) into an engine, it would burn hotter. That gives you a cleaner burn of the hydrocarbons, alright, but raises problems of NOx production at those higher burn temperatures. SO you're trading one form of pollution for another.

if you have an efficient NOx clean-up system, then you may get away with it (or if for some reason you're in an area with a partly-burned hydrocarbon problem but no NOx problem). Otherwise, it's a fraud (but not neccesarily a scam - the poor deluded engineer might actually beleive his own hype!)