Champion Generator not even close to rated output

"High altitude jet kit" is to keep the RATIO the same, not the amount of fuel.
Octane is only a measure of how fast the fuel burns. Higher octane slower burn rate, lower octane faster burn rate/flame spread.
High compression engines need slower burn rate to prevent "pinging".
The higher power is generated with the higher compression not the high octane fuel. If you get the compression high enough you will have a Diesel engine.
These are ignited by the heat only from the extra high compression.