come on, really?? the sound alone is an upgrade!! but yet they are lighter and they do perform better
typically a 3-5 rear wheel HP gain with pipes and DP ECU, improved torque as well. But the real gains will be felt if you take the next step and Dyno tune the bike with either one of the new tuneable ECU options out there or the use of a PC3 with custom dual map tune..
Here is a good example of the potential percentage of gain if done right, the first run was stock. Not a 1198 but only a S4R but the % of gain is what is impressive