I just put in an AFE CAI (
www.afefilters.com) and it seems to work pretty well. Haven't had in on a dyno, but the car is definitely snappier. Didn't have to reflash the computer. In fact, I got the kit at my friendly Ford dealer's parts dept. Also have had the car serviced there...no hassles about mods voiding warranties. I think the
K&N CAI also doesn't need a reflash.
I think it was MM&FF that had a shoot out of a bunch of CAIs. They all seem to work and give from 15-20 HP.