Gy6 150cc runs great for 2 miles then I feel power loss?

[thesampson22]

I could really use some help with this problem, I just had the motor rebuilt and the carbs cleaned and jetted. I put a race plug wire and coil and a performance CDI box on it. I just put 500 miles on it since the rebuild. a couple days ago when I was out riding it the motor started to decline in power and took a long time to get up to speed. when I'm going about 45 miles per hour and I let off the throttle and then I roll on the throttle again it feels like the motor cuts out for a second and then comes back on. it idles just fine when I'm sitting at lights but then take off becomes a little laggy and sometimes it feels like the cylinder misses or misfires. I ordered another performance plug and coil and put it on the scooter but it still does this power loss thing. Help Please!!!