ok ive got a AEM cold air intake and my filter is all bettin up so im going to a k&N filter what size do i get or do i even get a K&N filter

 

Any filter will do as long as it has the right intake cone size to adapt to the aem piping size. They even sell cheap ones at pep boys, but i wouldnt advise on those. But measure your piping size then go here and match the one you need
http://www.knfilters.com/search/univcone.aspx

 

you can get a K&N cone filter that will fit (that's what i used on my AEM CAI) ur CAI at autozone or advanced auto for like 40 or 45 bucks.