Hi Richard.
I discovered last week that the stock silencer I acquired last year is from an 05 model. The cat part is in the link pipe itself, not the outlet from the EXUP collector box.
If you remove your silencer you'll see the cat consists of a circle of about six to eight 1cm diameter tubes which are tacked welded to each other. I haven't looked deeper inside with a torch but it looks like the whole assembly is held in the link pipe by a couple of tacked tags. Should be simple enough to remove but it doesn't look as though it's restrictive to any significant extent. It's certainly not the dense honeycomb assembly we typically associate with cat cons.
Frankly, I see no point in trying to remove the cat from the stock silencer. If it's performance gains you're after, you would be slinging the whole lot under the workbench and replacing it with a slip on.
As for the ECU, I suppose there might be minor changes to the ignition timing but I don't recall anyone reporting different power output figures for the 05 model compared with the preceding years.
RMWL