These engines can be identified by smooth valve covers, plug leads and a wasted spark coil in the middle of the intake manifold. In addition, the inlet manifold may be bare aluminum for all WRX models and red for all STI models. The engine utilizes an IHI ball-bearing turbo unit. VF22 on the WRX, either a VF23 or VF24 on the STI. These engines have die-cast pistons for all WRX models, STI and STI typeRA/STI type R models shares exactly the same factory forged pistons.