Considering 2018 Subaru Impreza STI?

Originally Posted by Chuck33079

It's not an issue about it leaning out when you add mods. It's the factory tune. Your 2003 did not have the same problem since they had a decent tune stock and kept emissions in check during spoolup with a cat in the uppipe. You could actually get away with a full catless exhaust on a 2002-2003 motor with zero issues. This issue started around 2008 or so. If you're ok with the potential warranty problems, give it 1k miles and reflash it. Otherwise wait until they do something about that motor. Personally, I'd stay away unless you're planning on such heavy modding that the warranty would be worthless anyway.