HKS Exhaust Manifold - Unequal Length Header - With Cat - GT86 & BRZGT86 HKS Super Manifold with Catalyser Boxer Spec 4 1 Design Unequal Length With Cat 60mm pipe diameter The HKS 4 1 manifold is un equal length and produces more power in the mid range along with the "boxer sound". With tuning this manifold can significantly reduce the "torque dip" associated with the stock manifold. Includes alloy bungs to delete noise generator Fensport Tip: For the best result, Ecu will require tuning, we recommend our GT86 & BRZ