AWI on the Dart and garrett is meant to cool the incoming air charge, and by doing so improve the density/mass airflow this allows more fuel to be burned without exceeding temp limitations. Nox cools the incoming charge, but the largest reason for increased performance is that it has a higher percentage of oxygen allowing , once again more fuel to be burned. This makes more sense in a piston engine as to make the most power a stoichiometric mixture must be burned around 14.7:1 air/fuel. most Nox systems actually have a dual system with both fuel and Nox injectors. injecting Nox on its own without a commensurate increase in fuel will increase temperatures and cause detonation. In other words eat your engine