The common usage
In general use, Stage 1 means the vehicle keeps its original hardware and only the ECU software is revised. Later “stages” usually imply hardware changes such as intake, exhaust or turbocharger work.
Because no body defines these terms, two Stage 1 maps from different providers can be very different in ambition and judgement.
Why we describe the work instead
Rather than selling you a label, we explain what is available for your exact vehicle and software, what we would prioritise given its condition and use, and what we would not do.
That is a more useful conversation than a tier name, and it avoids implying that every vehicle gets the same treatment.
What stays constant
Whatever it is called, the condition of the vehicle decides what is sensible. The health check comes first, and no figures are promised without genuine data for your vehicle.