Originally Posted by AlpineSwift
The aFe is really a hit or miss. You either get it right or get screwed. Unfortunately, I've been screwed.
I used to think like some of the above posters but for the most part AFE is a huge miss. Problem with AFE is the heatsoak that happens at low speeds, especially on take off. At low speeds the intake is pulling hot air from around the engine bay and there is no way to avoid this. A guy I work with also had the AFE intake and reported the same exact problem. At take off the AFE will make your car run sluggish and that's pretty much a given for everyone.
Also I'm no engineer but pulling in more air is not necessarily good, especially if your car is not mapped for it. I'm guessing this is why many AFE intake users tend to get the "engine running rich bank 2 (or 1) code.
And if you think about it both the stock and perfromance BMW intakes are CAIs. Both are set to pull incoming cold air and completly sealed from the engine heat. The AFE cai is situated in a position were is has no choice but to pull the hot air in.