I just did this for my '07 yesterday, so I can give you some feedback.

I only made my own filter because they changed the shape for '07 and the filters don't seem to be available anywhere. My local Ford dealer (hybrid certified) said they couldn't get them and had never seen one.

So I went to Lowes and got a $15 3M 20" x 20" furnace filter with the chicken wire on both sides. Filter box came open per the instructions and I laboriously made a cardboard template that would fit into the box. With the template I then cut the furnace filter to shape leaving it slightly oversize (1/8") on all sides. The filter is a hassle to cut cleanly, you need both tin snips for the wire and scissors to cut the paper. The edges were not particularly smooth but I didn't tape them yet.

I tried the filter in the filter box and it fit quite well, and the rough edges could be tucked in making a nice tight seal. Taping the edges was not necessary in my case and would not have improved the fit or sealing.

On the '07, the filter box is made of black plastic with a wire mesh covering the air intake holes. This wire mesh is anchored by melting the plastic filter box in spots. Looking at my box, the wire mesh was a bad fit and poorly anchored, but too secure to remove. So I took a soldering gun and tacked down the wire mesh to the filter box in a few more places to make it tighter.

That's it. Took about one hour. The '06 should be easier because your filter is rectangular. But your filter is also readily available at auto parts stores, so you could even buy one for now and use it later as a template when you change it out.

Attached Images

Cabin Filter.pdf (189.8 KB, 69 views)