Hi bmroxm5 i think I have worked it out.
I did a search for my exact car on RealOEM and show my exhaust here:
I cant seem to understand all the part numbers but it starts that 02 exhaust is 70mm - there is another version for 65mm also. Also mentions somthing else for M Sports package (which I have) but not sure what it means.
When i was looking at the exhaust page I believe that the CAT converts are actually built into the exhaust manafold for my E90 - Have a look here:
So as long as I am not removing my CAT (which you confirmed in a center resonator) I should be able to plug and play via the US version.
bmroxm5 - you seem to know your stuff so let me know your thoughts
I would prefer entire OEM rather than going to the exhaust shop to cut things up.