Great info, thanks guys. I looked closely at euro stock mufflers for sale online they look the same as my japanese one with a larger inlet that goes in at a different angle and place to the US ones. The outlet to my headers is 2.5" diameter, just like the euros. My headers also appear to be aftermarket after a comparison with another japanese imported bike I saw today.
I wonder what the colour of mine is all about?
It appears to be a US bike built for Japan with aftermarket Euro spec headers now in New Zealand. No wonder it confused me :p