I took my car for MOT on 25/10 and unfortunately it failed for CO emissions. I was advised to options to get Cataclean and drive car on high revs. I tried this and came back on 26/10 - CO emission readings were checked by Simon and Richard, they were low than day before, so I was advised to do another 30min drive on high revs, I came back and result was the same. Then Richard & Simon tried various options as they believed car of this low mileage should not have CO emission issue, but result was not good. Then Richard tried some other options like tightening the spark plug screws, allowed natural air to pass through etc and guess what - CO emissions were reduced and MOT passed.