I bought a au S1 wagon and the bug got me and I went to a wreckers and talked to a bloke about the XR6 S1 and he told me that the only difference is the ECU and Gear box comp is that true or is he full of it as I did get the ECU and fitted it and there is a differance,It is more touque and holds gears alot longer .
Thanks any info would help.

there might be a difference in the heads, slightly more ported than standard, valves, springs, etc.
thats the difference in the E series falcons so its probly the same in the AU

different cam and springs, also injectors and fuel regulator possibly