This is fine with me and I am not doing this because I am trying to counter you, or negate your experience with so many of these engines.
I also have seen with my own eyes the differences in the timing and AVCS maps, as compared with the USDM Sti maps. There is a reason for that, it may be the fuel, maybe California fuel compliance, one can only speculate.
Not to mention that USDM Sti stock seem to have problems and in the past have knocked.
I am trying however to run the paper trail, to find out what these cars are designed to run on.
In this day and age, the facts can be established, no speculation is necessary.
In my research, the previous post, I am not typing my opinion, I am only bringing facts. You don't have to believe me, just click on the link and use google or bing translator.
I also have a 2005 Spec C owner's manual in pdf in japanese that I'm trying to translate, but bing does not take my paste from PDF right now.