Might be worth a bottle of ignition system cleaner too. Forte Advanced gsa formula or Forte ignition system cleaner maybe? The local garage (who also MOT) swear by it. I've used it on my 1.8 mk3 Golf (not for MOT purposes's though) and engine does seem a bit smoother.
I think (from memory) the high CO is rich running? Might be worth looking at the coolant temp sensor - though i'd assume it'd be rich at natural idle too. Maybe the air filter needs replacing - did you replace that already?
Cheers - let us know how you get on?
Edited by Javalin on 14/04/2009 at 13:54
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