You quoted "as the ECU may have Adapted to old cat".
Please explain your reason for this I think it as no substance what so ever......
I.e this car will only have a Upstream Lambda sensor , so the ECU has no way of checking the CAT performance.
And Even if it had a Down stream Lambda sensor , its only there to monitor the the CAT efficiency no adaption will take place, unless you have some new ground breaking information.