HKS Extension Kit w/ Cat | Toyota 86 / Subaru BRZ / Scion FR-S (12-21) (11999-AT002)HKS Extension Kit w Cat Part #: 11999 AT002 Overview The HKS Extension Kit w Cat is an advanced exhaust component designed for Toyota 86, Subaru BRZ, and Scion FR S models from 2012 to 2021. This kit features a specialized design that utilizes an individual main port (turbine exhaust) and bypass port (wastegate actuator) to optimize exhaust flow. Its primary purpose is to reduce exhaust gas interference, resulting in a smoother and more efficient