Neither the uneven idle (just uneven, it is not 'hunting' as we used to call it), nor the rich idle mixture result are new, I think it has always been like that. I was just prompted by the tester this time to think that maybe a rich idle is bad for the engine? Bore wash? Why wouldn't CC set the idle better if it has always been like this, and if it is like other 7s, how do post-98 cars pass the MOT?