Just fitted a K&N panel filter to my 2.0l weekend.

WOW! what more can I say, it's a damn sight quicker than it used to be through the gears and has got rid of a couple of flat spots that i had!
Got to be worth the £30 I paid as you just wash them out and re-oil them rather than repalcing every 12,00 miles!
Just have to wait and see how much better the MPG is.
I managed 29.5 mpg on a motorway run at the weekend.