I'm working on creating my own version of this as well. Instead of having to use two of the 3" spectre flanges (because of the small gap around the edges in the stock box) I looked and found a 4" inlet flange that I am hoping will work instead. http://www.amazon.com/gp/product/B00...00_i00_details
Now if the damn thing will ever ship..
I looked on K&N's website and there are a couple filters in there that I believe will work. I'm just waiting until I get the 4" flange and see if it will cover the hole in the box completely before going forward with it. I plan on using some rubber gasket between the flange and the box to make it air tight. IF the 4" part works, the added benefit will be the smooth air intake tract in the box, and no need to worry about the mas possibly being affected from disrupted airflow.