MISHIMOTO Subaru WRX/STI Ignition Coil, 4-Pack 2004-2010

A properly functioning engine relies on fuel, air, compression, and spark. Before increasing power output, it is essential to ensure all maintenance is current and each system is operating as intended. Weak spark delivery can lead to misfires, rough idle, reduced fuel economy, and catalytic‑converter damage, all of which diminish performance and drivability. Establishing a strong, consistent ignition signal is a critical foundation before pursuing further modifications.