Thanks guys, appreciate the help. Yup had the code before. Have rest the light and it has been months since it relit. I have a decat and aftermarket exhaust and intake, perhaps it's time for a remap.
I have a standard mid-section of exhaust. Been told to change this first as rest of exhaust is aftermarket.
I am guessing that standard section will be smaller bore and therefore restricting flow still, so not worth remapping yet.
I reset the code again this evening, hopefully it will remain unlit again for a long time.