It was true that their car didn't experience gains, not all cars do. Look at the 3.7 and 5.0. With just a CAI there isn't much gain. Same with a Honda S2000, some cars just have better factory intakes than others.
Typically older cars benefit more from a CAI than newer ones. The newer cars are built for engine efficiency so they typically have a good intake from the factory.
99 Chevrolet Camaro Z28 M6 - 6.676 @ 103 in 1/8, 10.512 @ 130.2 on street tires, H/C/I
93 Eagle Talon TSI AWD 5spd - Built 6 Bolt, 16G Evo3, HKS 272 Cams - under construction
94 Mustang GT - 5.0 bored and stroked to 347, Vortech V1 @ 10 PSI, Tremec TKO 600 - PIA