"The Lancer platform was completely changed in 1996, and along with it the Evolution, which had become extremely popular throughout the world. The engine and transaxle was rotated 180° to better balance the weight and eliminate torque steer. There were two versions available, The RS and GSR. The RS version was produced as a competition car with a limited-slip front differential and a friction type LSD at the rear. It also came with GLX seats and a choice of either 16" or 17" OZ light weight racing wheels. The RS also had wind up windows, optional air conditioning in some models, and a few extra brace bars to strengthen the chassis, one behind the front grill and the other across the boot floor. The RS also had thinner body panels and glass. The GSR and the RS shared a new twin scroll turbocharger which helped to increase power to 280 PS (206 kW; 276 hp) at 6,500 rpm and 330 N·m (243 lb·ft) of torque at 4,000 rpm. Mitsubishi's new Active Yaw Control appeared as a factory option on the GSR model, which used steering, throttle input sensors and g sensors to computer-hydraulically control torque split individually to the rear wheels and as a result the 10000 Evolution IVs produced all sold quickly. The Evolution IV can be distinguished by its two large fog lights in the front bumper (option on RS version), and the newly designed tail lights on the rear, which became a standard design to Evolution V, which would become yet another trademark of the Evolution series. This new generation was slightly heavier than previous Evos—the GSR in particular due to the added technology systems—but to counter this the car produced even more power—the weight of the RS being 1,260 kg (2,778 lb) and the GSR being 1,345 kg (2,965 lb). Much of the technical improvements for this generation were also used in the second generation Mitsubishi RVR sold only in Japan. The lancer evolution 4 had problems with the rear diff as it was very weak, and also had problems with big end bearings.