Theres no such thing as stages anyone who sells that sort of thing its a gimmick to sell things to people who dont know any better and when it comes to tunes off ebay pr the like you'll find most of themare waste of money and petrol and probably wont give you anymore power.
Memcals is what holds the tune for engine. Any mods such as a cam, injectors or raised compression require a retune to maximise the performance from the upgrade. Aproper tune will be done on a dyno using kalmaker or such then a new memcal is burned and installed in ecu when tune is finalised
For example if you put in bigger injectors without a retune, the ECU assume theyre still stock and will treat them as such but in reality your actually putting more fuel in when its not needed so your wasting petrol