Why do some vehicles show Stage 1, 2 and 3 without hardware requirements?

Manufacturers often use the same engine across several models and sell it at different power outputs, with the lower versions limited by software alone. On these vehicles, our stages follow the factory power levels instead: Stage 1 brings your engine up to the next factory output, Stage 2 to the one above that, and so on. The final stage takes the engine beyond the highest factory figure. No hardware changes are needed for these stages unless the product listing says otherwise.