peugeot speedfight 1 power problem?

I have a peugeot speedfight 1 1998 model was working fine until i wen to tune it up so i bought a leo vince exhuast which came with clutch springs and rollers so i fitted them went take her for a spin and hardly no power to take of and then you get a blast of power but still not at top speed so i read on the internet that you need to put in a jet in the carb, so i put back on my old parts but still no power help..?