XK8 catalytic converter

[paulXK8]

The cats on my 2005 XK8 (X100) are not working properly. It's had the diagnostics, temperature before and after check, etc. The problem is that no one seems to have cats for the 4.2L engine. I see that there is some previous posting on this issue but no conclusion. There are cats for the 4.0L engine available. Has anyone successfully modified these for the 4.2L engine?