I also have to disagree. I've seen dyno results in a lot of aftermarket stuff that prove gains. A solid CAI, Cat-back exhaust and tune all work very well together to greatly improve the feel of a vehicle. Will these add ons shave seconds off a 0-60 run? Most likely not much more than a few tenths. However, for me the difference is all in how the vehicle actually feels when I am driving. If I can feel these mods working when I drive around town and when I press the gas pedal then I am happy.
It's like the "Yanny and Laurel" sound clip video from a few months back (Google it if you dont know what I am talking about). Some people hear Yanny, and others hear Laurel. Some people can tell when they mod their vehicle, other people can't. To each their own.