Hi All,

I have an interesting frankencar situation that I'm trying to figure out. I recently purchased an old project car with a JDM EJ201 engine of unknown miles or origin, and the ECU is from a 2000 legacy with the EJ25. I have been having odd issues with idle, and occasional codes for EGR, even though there's no EGR on this EJ20 engine. I have also read that this mismatched ECU combination can cause rich running conditions or eventual engine damage? My thought is that I need to swap out the EJ25 ecu with the correct one from whichever car and year this engine came from.

2 questions really:
1 - How would I ID which model and year this engine came from in order to get the correct ECU?
2 - Will the correct ECU be plug and play with the current wiring harness or will I need to make a new one?

Any help is appreciated, thank you so much!