3MI Hose Adapter w/ IAG, Cobb, Crawford AOS Adapter - AOSHOSE-IAGPut simply this hose is used to improve the oil return from your AOS so that it can better perform for you. So what's going on? Many drain hose installations have the drain hose close to horizontal or with very little vertical angle. Under acceleration this prevents the oil from freely draining back to your sump. It is also well documented that EJ engines, under heavy cornering, push oil into the heads and can lead to excess oil entering the AOS.