Passed the MOT this afternoon at 4.31% co
Took the car for a drive round the long way to get to the garage and then with it idling connected to the emissions tester I leaned the mixture out gradually until the above figure was reached. Didn’t run out of adjustment, so I didn’t need to resort to removing the airfilter or anything like that.
Success! Thanks for your help all, much appreciated.
Cheers