Thought I would share this. I bought a K&N filter for my 05 4.6L F150 to help it breath better. I went one step further. Rather than spend $200+ on an AirRaid system I decided to modify the stock system to allow more air to enter the filter. I drilled 9 (8 on the front and 1 on the bottom) 2" holes. This allows the box to "catch" air and the back is still solid which blocks some of the heat from the engine. There was a noticable improvement in throttle response and the last two tanks of gas averaged 2 mpg better than before the mod. I know this is minimal but it won't take long to pay for the filter plus it just feels peppier. Here is a pic of how the box looks. $35 for the filter and about 15 minutes to drill the holes. If you have an F150 with this style airbox....I highly recommend it.