We offer Akrapovic Racing and Evolution systems with a HEXAGONAL muffler to complement the aggressive lines of the Yamaha. The systems differ only in their selection of materials, while both offer the same performance injection guaranteed to satisfy all racing-oriented riders. The Street Legal versions of the systems come with noise dampers and are approved for street use.  Measurements of the Akrapovic EVOLUTION system on the YAMAHA FZ1 (without muffler insert):  Power & Torque: the Akrapovic Racing and Evolution systems make the engine massively more responsive, as is clearly visible from the power and torque curves. Both max. power of 146 HP and max. increased power of 10.7 HP were measured at 11200 rpm.