The ECU does indeed have an unique ECU mapping, but it's only 1HP different from the "standard" ECU mapping. If you're getting one replaced / repaired, it would probably be worth going for one of the modded maps which gives you even more than the 185BHP of the original CSK.
Springs are the same as for 4 doors of the same year. Infact, the only spring specification change seems to have been at VIN GA464553. (there's one spec before that VIN no, and one spec after that VIN no)