Here is a free fix that I made, because I have found all of these fixes interesting but have always considered the stock filter to be a very good quality filter and I did not want to switch to a paper filter because the oiled foam filters are superior for blocking dust. This is very simple; check out the attached photo's. I took a piece of scrap 2X4 and cut it to about 5.5" then wedged it in behind the filter and marked it for depth then cut it for depth so that it fit in flush (see 1st photo). Then all you need to do once you get a good tight flush fit that pushes the filter forward nice and tight is trim the 3 posts flush off of the top cover so they just slightly touch or push down on the wood block. Now you have a nice tight seal at the air intake. If you want added air flow around the back side of the filter and air box, just drill some half inch holes in the block, as many as you like, 4 or 5 should be sufficient.