HKS Equal Length Header / Exhaust Manifold | 2008-2021 Subaru WRX STI14019 AF002 SUBARU IMPREZA 2. 5i GT 4D 2009 2010 EJ255 You can have the great performance and great muffler sound of the isometric layout by changing exhaust manifold only with the stock oil pan layout. You will notice immediately the new exhaust sound and the AT vehicles paddle shift gear down feels very cool. You can enjoy the GRB as AT vehicle. The gas pedal response is more sensitive, so its much easier to control.