Hi. Got myself a Seat Altea XL diesel 2006. It’s not a smoker and runs really well. However, Just put it in for a MOT and it failed the emissions check. Took it away and fitted a new air and fuel filter. Put 2 lots of Wynns diesel engine cleaner at two different times over the course of a week, ragged the bones out of it the morning of the retest and it failed again. Only thing I forgot to do is put some non supermarket diesel into it. Not sure how much of a difference this makes. Any help advice would be greatly appreciated
