The only info we have is what was released, no detailed pics of the exhaust system. I have no idea if the piping diameter changed, etc. US E46 M3's also had cats integrated into the header and there was power to be picked up by going aftermarket.

 

I thought there was power to be gained before they were integrated. What exactly do you mean integrated? Similar to the turbo?

 

What it means is the primary cats are one piece with the header. The cats are sitting pretty far upstream.