What do different ECU do? and what types can you get for my car, is it work the money?

People say if you';ve put a stage 2 cam in your standard car it'll run better with an XR6 ECU (i'm presuming I6), not sure what the deal isi with the souther african ones, but the pursuit ones and XR6 ones take away speed limiter too and change gear shift patterns..

first question before anything is, what have you done to it so far?
you can get power without the ecu being touched .. if u want a large amount of power youll need the same money for ecu setup as for the engine rebuild