Re: "Fuel Only"
Since the engine came factory equipped as a turbocharged engine burning diesel fuel, I don't see it as an additional way to make power.
The biggest thing is injections. Aka, drugs. "Fuel only" means that the only thing your using other than normal atmosphere is diesel fuel to make the power. When you use concentrations of nitrogen and oxygen and inject them, you have strayed from that. When you introduce propane, you have strayed. When you introduce methanol same deal.
Fuel only means diesel fuel and the air we breath and that's it. It doesn't matter how much you compress that air.