Ok, a few things to get straight.
1st:
Japan uses a different method of testing for octane.
The pump octane is also referred to as the Anti-Knock Index (AKI). AKI is determined based on an average of the Research Octane Number (RON) and the Motor Octane Number (MON). The formula is RON+MON/2 normally abbreviated as R+M/2 on the pump.
The MON is a measure of the gasoline's ability to resist knock under sever operating conditions. MON affects high speed, part throttle and performance (under load such as in passing). The RON on the other hand, is a measure of gasoline's ability to resist knock under less severe conditions. RON affects low to medium speed knock and engine run-on (dieseling). For a given AKI, RON is typically 8-10 points higher than the MON. As an example, 87 AKI (pump octane) fuel would have a MON of 82 and a RON of 92.
Japan only uses the RON method, giving higher results. Its the same octane rating, just a different number.
2nd:
The 4WS has NOTHING to do with the ECU. The 4WS has its own computer in the trunk, there are no wires that connect the two.
If you have an ECU from Japan with an extra connector, to the best of my knowledge, you have an ECU with Traction Control.
That is the 4WS computer in my trunk.
Thats my JDM ECU (its says 2W on the side , not shown)
3rd:
Ofcourse the JDM engine is going to be faster, it has a .6 higher CR and the fuel and ignition maps to back it up. Japan doesnt have the same emmisions testing as the US, they most likely run a little phatter over there. I get about 19mpg city and 26 hwy at the most with my JDM H22 and JDM ECU.
Not trying to flame anybody, but reading post after post of wild speculation is like being over an H-T.com
EDIT: CR mistake. see below.