Gilera runner 180 top speed problem

I have a runner 180 2t. I had a lot of problems with the old ignition so i put on the 125/150 ac stator magnet black cdi and ignition coil. The bike runs great now a lot better than with the original ignition. It wheelis when i just pull the throttle. But when it reaches 90kmh and i pull the throttle it just feels like it cut out and if i hold the throttle it starts backfiring. What could be the problem. I didnt have that problem before (the top speed was around 130kmh) but i started having that problem when i still had the old ignition.