You need to go to a better MOT station...mine will adjust the CO2 level whilst they test it :dance:
You need to unscrew the adjuster on the airmass meter to get the correct level....too lean and the gases will be too hot. Best suggestion would be to fit the windscreen (easy enough to do by removing the centre strip, push out the glass and reverse process to fit the new one. Parachute cord helps lift the rubber over the glass. If non available it can be done using thin blut objects to lift the rubber) and ask the mot tester if he would tweek the mixture when he does the re-test..