I bought the Perrin drop in just because I bought it at the same time as the single piece down pipe. The K&N should be just as good if not better from what I hear. It's way better than buying new paper ones!
just got my car back, dropped in my AEM CAI and let me tell you, there is a noticeable difference. Running XPT Stage 2, which has a tune specific for this intake. I had a nasty exhaust leak that has been sealed as well but the car just feels like it accelerates easier. Throttle response is alot quicker, which is the opposite of what i thought would happen with the extra piping. It also helps at the higher rpms and the drop in boost is less noticable. just seems smoother.
I just ordered an AEM CAI and i have read on different sites that it wont mess up the MAF reading because its the sam size in diameter as the stock one. oh and as for the gains, on a wrx they say its anywhere from 13-19 HP and for the sti its anywhere from 25-38 HP. I cant prove it, its just what i read.
The check engine light will come on if there is a lean condition so you will know about it. The ECM will compensate and add more fuel if more air is being introduced. There is a certain percentage that it will compensate, and once the percentage is exceeded then the check engine light will come on. Then you will have a lean condition code. Thats my theory from someone who has spent to much time in school to learn all this.
Headed down to the shop after work to get the AEM CAI for my 2010 WRX Hatch. I will keep you updated as well. Doubt the power increase they claim, but there is only one way to find out. First performance mod to the week and a half old hatch...only thing I have done so far is limo tint the backs, dark on the front. Looks pretty sick!
The problem with the claims they make is they slap the intake on the car, then right on a dyno. The car doesn't adjust for the increased air right away, so the first pull runs lean and makes more power. Once its been going a few times the gains are minimal.