I went and made a custom setup for my truck because the stock airbox liked to suck up water. The setup I have now sucks "gasp" hot underhood air, maybe someday I will revise it so it draws cool outside air. I have noticed absolutely no difference from the stock airbox setup as far as power output or throttle response. The setup is actually a stock airbox out of an early 90's mitsubishi montero, It runs the stock paper filter from that setup as well. I can get a k&n for it for free (uses the same filter as an early eclipse) but I choose not to because the paper filter is still clean after nearly 40k and it filters just fine. The 2.9 doesnt suck very much air at WOT ( i believe its under 250 cfm but don't quote me on that). As long as the stock system is capable of flowing that amount or above, going to a more "free flowing design" is pretty much useless for any other purpose than making you feel special.