Emissions is an issue when trying to get through the annual MOT! I've only had problems before when my old Civic used to leak through the join in where my de-cat/cat pipe went in, which resulted in it failing the emissions test. But exhaust sealant sorted that out. I also re-welded all the joins in the full exhaust system to be sure they had no leaks.
What were you thinking about with the emissions on this one?