[dcb]

As far as I can tell though it takes some serious engine and electrical system mods to even have a prayer of working, so I will be extremely skeptical of any bolt-on solutions.

plus it depends on if gas + hydrogen makes more energy than their individual contributions, which would be the case if the gas was not burning completely.

So if I were you, I would try to get a handle on how much unburnt gas we are talking about (and under what conditions), as that is where the gains, if any, lie. It is obvious that there is some unburnt fuel in many conditions as we need catalytic converters, and they get hot.

Weigh these potential gains (where you rebuild your engine and mill the deck for a high compression ratio and install a super efficient alternator) compared to something like converting your engine to an atkinson cycle with a new cam, where you simply give the fuel more room/time to burn and expand.