(2004 - 2009)  SP SERIES exhaust systems are more affordable versions of our exhaust systems, made of high-quality stainless steel. For the Yamaha we present the SLIP-ON SP SERIES, intended to provide aesthetic enhancement as well as a slight performance increase and sportier sound. The main characteristic of this system is that it contains noise dampers and therefore conforms to regulations for exhaust system noise levels for street use.      Performance  Measurements of the Akrapovic SLIP-ON SP SERIES system on the YAMAHA FZ 6, FZ 6 FAZER (without noise damper):  Power: as the power and torque curves show, the Yamaha engine opens up considerably with the Akrapovic SLIP-ON SP SERIES system installed. The power increase is shown from around 5000 rpm on and extends right to the top of the rpm range. Max. power of 96.4 HP is obtained at 12100 rpm, and max. increased power of 2.7 HP appears at the same rpm. Torque: the torque curve also improves using the new system. Torque is increased throughout the rpm range, especially in the middle of the range. This means more pull in higher gears without being forced to go to higher revs.