Please confirm - did you swap an STI ecu into a non-STI?
If yes, you need to change AFM and injectors as well at a minimum. You should also swap your turbo to the appropriately matched STI variant (likely a vf28) and run an STI intercooler.
You also need to make sure that the ECU you've swapped from was mapped for the same compression ratio as what you're swapping into as there are differences between some WRX and STI builds/years. E.g. some WRX were 9.0:1 yet the STI variant was 8.0:1 (or 8.5:1 - can't remember exact numbers but the point stands).
Someone else will be able to elaborate on this more than I can