also a stage one map is a generic remap as in one size fits all, as the car left the factory it was set up to run on all grades of fuel in all climates. A stage one tunes the fuel/boost/ignition so that the engine runs more efficently hence makes more power but is still leaves room for improvement.
A stage two is a full custom remap meaning that everything is tuned to suit that particular car, as we all know two cars even if they rolled of the line after each other are not the same, so you CAN have a stage two on an otherwise standard car and it would improve the gains over a stage one, but for the extra cost involved for the extra 4-5 hp it would make, it's not really worth it and is better used when FMIC's, exhausts and filters have also been fitted.