*screams* I can't believe you put 91 in it
. I really don't know what to say to that. Jap cars were designed to have much higher octane levels in their cars (I think they have 102 there??) than what aus & US offer, which is why you MUST have the car tuned when you get it. Leaning out and/ or over boosting is going to destroy your engine pretty quickly. I personally would take it straight to a performance workshop with a dyno and have it tuned. Check what levels the boost is set to, I would reset them to my own.