I can't recall If this has been asked before, or else I wouldn't waste my time posting this. but I have an cheap Ebay CAI, I want to replace the filter with a K&N. does anyone know of the size I need to do so?
well if you want to waste your money, be my guest. 3.5"
I bought a new filter on ebay, just a 3.5" conical flter, and it had red cloth in it, and I was told this was the same cloth that k&n uses, so i essentially bought a K&n filter for $5, under a different name. (the one that came iwth my kit was really small, plus my dog attacked the one that came with it before I got to install it.....lol)
the reason your ford intake's K&N won't fit is simple...there is nothing to put a hose clamp on to attach it to your intake tube. Duct tape....if you're serious about that I wouldn't risk it. Duct tape is not good where high humidity levels are, or high heat...both under the hood. That along with the vibrations would most definately make the filter fall off and you'd be suckin up all kinds of sheit.