If you have an 02 GTS 6spd you can use an ecu from a 2000. Don't forget to replace the knock sensor too. I would imagine the people with a 05 could do this with an 03 ecu. You'll get about 800 more rpms in lift with this switch. Although, lowering lift engagement any further without F/I is kinda pointless because you have a dip in power.
No look at Wikipedia => toyota celica => europe and then the last on is thr most expensive one because it was a final edition i think and nicer body kit, leather/alcantara interior and much more, then the t-sport and only available in the UK