When I had my plus 8 emissions were always challenging. My tame MOT man would always do emissions first before starting the test proper. They were sometimes out of range, he recommended this stuff on a half tank

https://www.eurocarparts.com/p/cata..._znzeXYoCGsBZXlEqzsQhaho2D6jQmJ5WefjSZyk

And an 80 mile blast down the A55, back on the tester and certificate issued a couple of hours later

Make of it what you will


2012 Plus 4 in Sport Green. Much comfier than the Plus 8!