Originally Posted by northman
"the stock intake is great" is, IMO, one of the biggest wive's tales on here. With a VF on my 07, switching to an AEM CAI gave noticeable gains. Car spooled more readily, making more torque everywhere. The tuner stated that the later model intakes are even more restrictive, meaning there are more gains to be had.
Tuner also was emphatic that intakes must be tuned for, so either get protuned, or use a map specifically made for the particular intake you choose.
And don't cry about how you should only run a CAI if you live in a desert for fear of hydrolocking, if you don't drive through foot-deep puddles you will be fine. Course it never rains where I live, in Seattle.
It is great.
A lot of people jump on the, "Don't get an intake!!" Bandwagon because of the known issues running one without a tune. Some thought on that as well, the ECU has an easier time learning with the stock airbox during weather / temperature change and altitude change. Some say it's able to interpolate with the OEM box where as a CAI you may need a winter tune.
Also, the thought process of flow restrictions being the only reason to upgrade, IE maxed out MAF. That won't happen on a stock turbo WRX (08 and below at least).
With all that said, the stock airbox IS a great intake. There is data proving that a short ram will actually net you less power IIRC it was back to back dyno pulls with SPT SRI and the stock box but I recall seeing something along the same lines with the Cobb intake but I definitely could be mistaken.
Considering the nature of most of the import scene it is understandable to have the intake issue be something you research before you buy. A honda will benefit from a K&N autozone intake without question. Applying that mentality to FI Subarus is fool hearted.
Does it make sense for OP to spend $150-$300 on an intake and $400 on a protune? No.
The cost to gain ratio is no where near logical and that money is better spent elsewhere.
OP - In the end, it's your car and money so do with it what you want.