after posting this i just went to pick my wifey up from work, on motorway i floored in at 60mph in 6th gear and got severe misfire and very little acceleration! unbelieveable that it happens when i want info on when they should be changed. could it possibly be the cat? as this happened on another car of mine a few years ago (mg zr 160) just wouldnt go above 30mph that one. with the meggy now i can rev it and it seems ok, put go to drive it and its awfu missfiring! help!!!