Any of these STI ecus will be a better/more aggressive upgrade over the standard WRX V1-2 ecu, especially with the TD05. But keep in mind the yellows & orange didnt come around till V3+ so it wont run them to their full potential? (correct me if im wrong).
SA (STi chipped) - 1993/1994 STi
SB (STi chipped) - 1993/1994 STi RA
6K (STi mapped, but not Chipped) - 1995/1996 STi
7K (STi mapped, but not Chipped) - 1995/1996 STi RA
I managed to get an SA for mine & it made a nice noticeable difference but im still using the factory grey/green combo.