I have a 2003 2.6 saloon, and the last back box I fitted was actually a 2.2 back box, which many suppliers list as the same part anyway as the 2.6, having a single exit pipe. Mine fitted perfectly, and the exit pipe was the correct longer length, as some 2.5 boxes have shorter exit pipes which finish a little short of the bottom of the bumper cut out.
I also put a stainless end trim on it which neatly finished it off from an appearance point of view.
As I've got horse hair coming out of the back box, I was inclined to change it all from CATS back.
Is the entire 2.2 system the same as a 2.6 from the cats back please ?
The back box on the 2.2 saloon is the same as a 2.6 saloon with a single exit pipe, and fits either, whereas a 3.0/3.2 has twin exit pipes but will fit a 2.2 and 2.6 if you want twin pipes! The centre pipes (from the cats back) on a 2.6 saloon are the same as a 3.0 /3.2 saloon, but are totally different from a 2.2 (and indeed estates).