To say that there are zero gains from a CAI is pretty false.
There aren't substantial gains from a CAI but there ARE gains.
The OEM intake tract is VERY baffled. There are several resonator boxes connected to the plastic piping - each box will hamper the airflow and decrease noise. That is why with a CAI people will hear a more "agressive" sound. And, the same with the exhaust, when the resonators and bafflings are removed, gains can and will be realized.
The discussion on NASCAR engines with the tiny restrictor plates is 100% true and very valid. What it doesn't cover though, is the uniformity of the intake tract for those engines. The 2AZ has at least two large resonator chambers or boxes connected to the piping as well as that ruffled baffling which all somewhat impede airflow. Also, the most restrictive part of the OEM system (probably where the real gains will show up) is the OEM paper filter. That thing is really thick! Replacing it with a cone filter and providing a proper path for the air will yield at least some power advantage. I don't know how much (if any) gains can be realized from the "cold air" that is supposedly coming through from the wheel well. I would always recommend the GFI over any CAI but a CAI should show some purpose on the dyno.
CAIs can, however, be detrimental, time wise. Some owners have tested CAI equipped tCs with those nifty G Tech toys and found increases in 0-60 times. Some owners, looking to find real world advantages of the CAI, have raced stock tCs and found themselves coming up short a few fractions of a car length. Also, the reverse has been found to be true.
But regardless of real world times in street and track drag races, the gain in power will be there. The question really should be whether or not the power is useable.
My answer? For racing purposes, don't bother. For daily driving and some nice bling in the engine bay, it's totally worth it.