Speedfight 2 moped 100cc changed from standard exhaust to a doppler S3r?

ok i recently bought my self a doppler S3R exhaust so i changed it over and also rejetted my carb and i used some new rollers that they gave me with the exhaust but after doing all of this my moped now hits ful revs at about 20 mph but before it was topping revs out at about 50mph now it does eventually get to 50mph but it takes along time i have basically lost all the acceleration i had with my standard exhaust and im really stuck on what to do :/ please if someone could give me some pointers

thanks


Edit: ok so i put the old rollers back in and it does set off better but the speed and power is just no there im lucky to get 30 mph out of it i also deristricted the exhaust still no luck so i set off home from my mums house got half way there and it made a clunk and just simply cut out so then every time it fired up i get 100 meters down the road and cuts out again so im just stuck now any ideas

p.s i also checked everything and nothing is warn Sad