AEM's new Electronically Tuned Intake (ETI) Systems are raising air intake engineering standards once again. The FR-S uses a Mass Air flow (MAF) sensor to determine the air flow rate into the engine and meter fuel according to input from the sensor. The relation between the voltage output of the sensor and mass air flow is adversely affected by a shift to a larger diameter intake tube as the airspeed is reduced. This causes the MAF sensor to 'under report' air flow causing a lean condition at worst and a CEL at best. With a revolutionary ETI module and fully integrated design, AEM's air intake system adjusts the sensor electronically to read proper air density instead of using physical tube designs intended to "trick" the MAF reading. The result is bigger horsepower and torque gains out of an already very efficient engine: 10 HP at 6500 RPM according to AEM!