Black-wagon

Can anybody help? I have a 95 UK Wagon turbo, it's my first impreza and only had it a month. I still have a grin every time I drive it! To the question: I have found a second hand ecu from an early 96 impreza which is a V2 STI RA- ECU. Is it possible just to exchange the ecu's? Are there any possible problems and can I expect decent performance increases? The only other mods I have are an STI exhaust and K&N induction kit.