Now then Ray,
I wouldn't mind hearing from someone that has done the coring as they should be able to answer my question.
I wasn't thinking of coring the original exhausts as I need them for the MOT but I was looking to remove the catalyst to increase the air flow so I can use the standard exhausts with the Termi ECU & no lamda sensor.
You can see the cat when you take the silencers off & look down them from the engine side & as far as I know bikes are not tested for emmisions during an MOT so removing the cat shouldn't matter.