I am firmly of the opinion a low shot of NOS is the most reliable form of power adder on the H22A. Getting more then one jet is just as bad as getting different wastegate springs though
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I suspect something in the H22A's design makes it susceptible to detonation.. NOS is cold enough so a small shot isn't an issue if the gas is there.
There are one or two blown NOS engines, but that wasn't on 50hp shots. I don't know anyone who's messed an engine on a 50hp shot (due to detonation or melted valves). It would be possible with operator error or component failure, I guess, but unlikely.
Steve