hi folks-can any one guide me as to how to lower c.o idle,-car is a focus 2002-1.5 facelift model 1600 zetec,s petrol.seems the c.o is rising year on year at mot time.car has only done 49 thousand miles and has been regulary serviced-even when not due.many thanks if you can help.(I give it a thrash before going for mot to clear it out, because it is little used.)

As it's only CO and a small rise each year I'd say the cat is getting weak but won't be worth replacing until it actually fails MOT.  Would also be worth making sure there aren't any leaks in the intake air pipework though.