Thought id have a nosey at my airfilter whilst cleaning under the bonnet, noticed it has what looks like a k&n filter fitted in the box, this seemed pretty dirty so have just ordered a new air filter (standard one) is there any benifit in using the k&n? if so i may give it a clean and reuse.

On the use of K&N filters you will find several opinions, one group sticks to the normal paper filter as they think the gain of the K&N filter does not justify the cost. There are people that believe that K&N filters don't do as good a job in filtering the really fine stuff so that long term wear on the engine could increase. There are people who believe that the filter oil mucks up their MAF.

I use a K&N filter for two reasons, paper filters are more expensive here then a K&N filter (ordered from the Netherlands) and the local environment here has a high level of dust so regular changes (paper) or cleaning (K&N) is required.

As to the testing both official and not official of the K&N filters, I don't believe that the K&N filters, even if they let more of the ultrafine dust through, are detrimental to car engines, even in the very long run.

As for power improvements, don't believe it makes "significant" difference, at least I didn't notice any difference between the dirty paper filter and new K&N filter on mine.

On the MAF, not sure, I think if you don't "overoil" it, you will be fine and besides the excess oil will disappear quickly enough.

If I would be living in the Europe, I would not put a K&N in but run it on normal paper filters, unless the car was already fitted with a K&N. MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

Thanks for the reply, for the time being ill put a standard filter back in and see if theses any difference, is hard to actually see how dirty the k&n is due to it being dark in colour.