Cloning an ECU?

[mukcl]

Hello experts, sorry if this question is a bit obvious, but I am only just getting into the theme of ECU tuning etc.
I have a friend that got a ECU tuned in Argentina, and its wicked! I was wondering if its possible to clone his ECU, ie modify my ECU so that its like this?

Its a Subaru Impreza WRX yr. 2000

Can I do this myself? or are the companies that do this?
I am fairly comp. savvy...

CHeers!!

Mike