Power and emission problem
I have 56 plate 2.2jts 159 and I have noticed it has been a bit down on power. Nothing too noticeable and all the gauges and fluid levels are reading as they should. I thought maybe the exhaust had come loose somewhere so when it went in for the MOT I asked them to take a look. They couldn't see anything and the exhaust definitely isn't loose but it did fail on emissions, something I have never had a problem with before. It could be coincidence but I suspect the two are linked.
Any idea what the problem is or where to start? Would it be the air filter?
Thanks in advance.