Chip, I think Pinky will agree w/ me that CAI is the "most bang..." mod.
Pinky went w/ the Import Development CF intake extention - cannot dyno-prove improvement, but Pinky swore he felt more consistent pull.
I, on the other hand, went w/ AEM and definitely feel the difference, especially at low end. Manufacturer dyno shows ~5-6 hp/tq on much of the rpm range, and as high as ~9 hp/tq.
Comptech is also coming out w/ one but for some reason they are holding back their dyno graph even though they provided promising gain figure on specific rpm range.