Perrin Air Oil Separator - Neon Yellow - 15-21 Subaru WRX for TMIC w/o Eyesight - PSP-ENG-609NYThe PERRIN Air Oil Separator traps oil from the crankcase vents before it enters the intake, reduces carbon build up, increases intercooler efficiency, which reduces the chance of performance robbing detonation. Not A Catch Can The air oil separator separates the oil from the air while draining it back to the engine Swirl Pot Technology The multi layer baffle design forces incoming engine blow by to move rapidly across the baffles to separate oil from