I had the same problem, had no power or acceleration became boggy and would not rev up properly, it is because the fuel injector is broken, the air intake is mechanical but the injector is control by the ecu so when you open the throttle up the engine is being starved of fuel, bought a new one from a peugeot dealer for £88 was an easy fix from just taking the seat out and working on it from there. this should help. bike works perfect now top speed of around 75!!
Greg, August 2011