I recently purchased a 03 Evo 8. It has the typical bolt ons with the stock turbo and FIC 850 injectors. I read the rom that was on the ecu and it is a stock rom that has been tuned. I did some idle and cruise logging and found the low trims to be at -1% and the mid trims to be at -6%. From what I have found searching it appears that the generally accepted level is anything less than 10% is ok but less than 5% is good. Are these values good enough to start tuning wot or should I strive for better fuel trims? Thanks for any help.

 

I would personally leave it and just monitor it.