I agree with Humanoid. I did a K&N FIPK on my 3.4 V6 and my wallet got lighter, I didn't notice any significant or measurable gain. If I had to do it over again, I would do the K&N or similar drop in. The FIPK looks cool but not many people are looking under the hood.
It's just a hole you cut into the stock airbox - and use a deckplate so you can fill it in when needed. I've considered doing it, read a few posts of slightly better mpg and makes a slightly beefier noise.