I have the AEM/MAZDASPEED CAI with the air aligner thingy, and without the hydroshield doodad. Got it off ebay for $100. (GOD I love ebay...). I and a shop tech, noticed a slight hesitation when you pound on it below about 2500 rpm, but I believe this MAY be correctable via throttlebody grounding, and MAY exist on all of them. Unless I missunderstood some reading I have done, air velocity is king for low RPM and down low torque, and volume is king for high revving horses. I have the book upstairs, Ill have to double check. The bigger pipe and longer path WILL slow velocity if only from the added viscosity in the pipe. Im not a fluid dynamics guy, I understand what is happening, but I know I cant explain the hows and whys worth a lick.
DONT BELIEVE THE BS about it sucking in water when it rains. It sits about 6 inches off the ground, in the fenderwell. It gets plenty of air from the vents and from the bumper area, and I took the car thru about 8 inches of standing water (it was late, dark as hell, stopped raining an hour before, and it was on a blind curve) and it never noticed. Got clear, shut down, jacked the car up, and pulled off the cover. BONE DRY. You would have to drive thru retard deep water to worry about it, as In ROAD CLOSED deep. More likely SIT in it with water up over the top of the filter, because if its only partly submerged, its still going to suck more air the water. See a fish tank filter inlet. Thing will suck ONLY AIR if so much as one row of inlets is exposed.
Another mag did an install on an 09 recently (like a month ago...cant remember which) and added an AP. On the stock map, the intake alone dropped the 40 to 70 time by about half a second, and they made note of the same thing you will: With the intake the car doesnt fall flat on its face over 5500 RPM. My Dashhawk says it will spill a pound of boost at about 5000 from 16-17 to 15-16, depending on things, but holds 15-16 pounds from there until you get around to shifting.
I wont get into the whole CAI vs SRI arguement, other then to say that the SRI is probably better when you mash the gas down low, the CAI is probably better up top when volume matters, and when you dump 2 gears and blast off to go around something. But when you are simply cruising at 65-70 miles per hour, it doesnt make a lick of difference.
EDIT: Volume and velocity example: Dual upper intake runners from the SVT Contour. Long, skinny one for low down, kept velocity up for torque low, short fat one for top end high volume. Use a butterfly valve to open the secondary runners when needed. KNEW I I had seed a damn good example when I was selling cars lo those many years ago. See here:
http://www.stuff.to/svtbrochure/power.html