Hi Porsche Doc
The Cat Plugs are now supplied and fitted on October 1st. Fault Codes cleaned up, and the car now idles and runs as it should. Clearly when I asked you a few messages ago if it could be the Exhaust Oxygen Sensors, I was in a way right. However I was thinking the Senors were faulty rather than them getting too much oxygen!
Any way thanks for your guidance through this particular maze.
Thanks Big Bob

 

Anytime you replace anything over a stock sensor, most of the time...You will get a Check engine light.
From my knowledge & experiance.