Forgive me if this has already been posted somewhere, I want able to find it. I plan on swapping an Ej207 into my00 rs. I plan to keep the motor as stock as possible. So if I do this do I need to tune the stock ecu? Or is just safe to get it checked out.
Good info has already been shared but also keep in mind that an Ej207 is a JDM engine. That means the ECU is tuned to use fuel of much higher octane than what's usually available locally. 94 octane may be ok if you can get it but really you should tune it for North American fuel if you want it to last.
Hell, a V7/8/9 will be fine enough too if you really don't want to tune, but with those options it could be beneficial to tune it. I have seen a decent amount of knock on my V8.. but a lot of other factors went into that one.
Check out my journal, I've got a decent amount of info on this matter.