It’* more than just the temperature of the air a “CAI” allows for but also the volume and it’* ability to injest greater volumes of air increasing it’* ability to read cooler incoming air. Keep in mind, “cool” has to be used in correlation with the outside temps. If it’* 90* outside, the coolest air that’* gonna get sucked in, is 90*. However, compared to your underhood temps, 90* is like sitting in a refridgerator.
In a perfect world, a “CAI” would have it’* filter and/or snorkel at the lowest point and where the greatest volume of air can be obtained. However, we don’t live in a perfect world. Due to the packaging of vehicles, engine’*, engine compartment layouts, sheetmetal layouts, etc, we’re kinda limited.
What a “CAI” of any sort does is allow greater volumes of air to be taken in, due to larger diameter plumbing, smoother curves, etc. Due to this increased volumetric efficiency, it also allows your IAT sensor to react more quickly to the change in the air temp of the imcoming air. In which case, loosely defined, it is a CAI. Connecting a simple scan tool and watching your IAT’* can tell you a lot.
Both OEM and aftermarket setups are subject to the same underhood conditions. It’* the ability of the aftermarket unit with it’* improved plumbing, less restriction, and overall better design (as the OEM unit is designed with many factors in mind besides performance), that will get the IAT sensor to read cooler, quicker, while at the same time flowing better.