Thanks Beammer, hadn't thought about the temperature aspect. I ordered two new cats for mine after a series of problems, but they took ages to arrive, so decided to cancel and run without them. My MOT has almost a year to go, so have time to evaluate the performance issues before replacing them becomes a necessity. Right now the car is very, very fast 
but very very thirsty 
Am going to have the ECU set-up checked, as you suggest, to see if the air/fuel ratiios are correct.
Thanks again,
John
