The Akrapovic Racing system is a step ahead of the Slip-On system in terms of exhaust system modification. It delivers a major increase in performance, and looks great on the bike. The Street Legal version includes an approved noise damper and is legal for street use.
    
Performance

Measurements of the Akrapovic RACING system on the BMW F 800 ST (without muffler insert):

Power & Torque: the Akrapovic Racing systems completely fill the dropout in the middle of the stock torque curve, giving the BMW engine more even pull. The power increase starts at around 3800 rpm, and continues right to the top of the range. Max. power of 88.9 HP was measured at 8700 rpm, and max. increased power was 4.5 HP at 4100 rpm.