Radium Engineering Air Oil Separator AOS-R Kit – 2013-2020 Subaru BRZ, Scion FR-S, Toyota 86High powered modified 4U GSE and FA20A engines tend to generate excessive blow by oil and gasses. In these cases, an ordinary small catch can may quickly fill with oil and not be adequate. Like the Radium Engineering Dual Catch Can Kit, the AOS (Air Oil Separator) kit is responsible for keeping blow by oil and other pollutants out of the intake pipe, manifold, turbocharger, and intercooler during all engine loads. The main difference is that an AOS