I agree that a mac/bbk fenderwell style cai setup really has no advantage over the stock box with a free flowing filter. The one possibility being the inside of the tube is smooth and rigid whereas the stock tube is ribbed and flexible. However, there is clearly a gain to be had over an open underhood air filter. When I bought my car it had the stock air tube/mas going straight to a giant k&n filter. The car would bog once it warmed up and never ran quite right. I picked up a densecharger cai kit cheap and it DEFINATELY made a difference. I'm attributing this entirely to the change in air temperature to the engine. None of you can tell me you don't notice a difference in how your car runs on a cold fall night compared to a 100* summer afternoon. As noted already in this thread the stock airbox ALREADY DOES THIS and the only real reason to switch from the stock setup to an aftermarket cai is for looks. With that said I think a mac cai or powerpipe (which I have now) both look 10x better under the hood than the stock setup, and I have no regrets about buying them or listing it with the rest of my mods. Also, I think a lot of times folks will upgrade their mass air sensor and throw a cai kit in the car at the same time, and attribute the gains they feel/see to the cai. Most likely they're noticing the improved response of the sensor.