K&N Drop In Filter 2008+ Subaru WRX / STi

Easy to install and you can hear the air being pulled in right away on your first drive.

My first suggestion, pick up two of these. It is very nice to be able to have a clean one sitting around to swap into the car vs waiting for your single one to dry. If you have two you can pull one and have time to clean it and let it dry for the next oil change. Seeing as how these are not that much more then OEM filters that only get one use, your spending will be justified quickly.

I have been using mine since 2009 and have had zero issues. Even if you only have one filter it is easy to clean, dry, oil and install when changing your oil. But do yourself a favor and grab 2.

I would also suggest spending $6 on a can of MAF cleaner and cleaning your MAF with every oil change as well. This will help the car run at peak performance.