KYOSTAR Valved Sport Catback Exhaust System for BMW G90 G99 M5 S68 4.4T Twin-Turbo V8 Engine The KYOSTAR Valved Sport Catback Exhaust System is designed for 2025+ BMW G90 M5 and G99 M5 Touring models equipped with the S68 4.4T twin-turbo V8 engine. Developed as a high-performance exhaust upgrade, this system improves exhaust flow efficiency, enhances the aggressive V8 exhaust character, and provides adjustable sound control through an integrated valve system. Manufactured