Perrin Air Oil Separators for the WRX/STI are a great product if you want to increase your intercooler efficiency and stopping oil from entering the intake. By reducing the amount of oil that is entering the intercooler and intake system you will have a cleaner more efficient motor and less engine damaging detonation. The Air Oil separator is a great item to have on highly used daily driven cars or complete race cars. Black or red the AOS are a clean easy install and easily maintained by taking off a single bolt for cleaning.
Note: For use with aftermarket FMIC.