What is ECU tuning and why does it matter for JDM cars?

ECU tuning remaps the engine control unit's fuel, ignition, and boost maps for your specific hardware setup and fuel quality. JDM cars were tuned for 100 RON Japanese premium fuel and metric temperatures; a proper tune for US 93 octane and your local conditions can add meaningful power and drivability. Standalone ECUs (Link, Haltech, Motec) replace the OEM unit entirely for maximum tunability; piggyback ECUs modify signals without full replacement.