Change exhaust, and too poor blend of fuel

[LaTiz]

Hi, a few days ago i mount in my '02 FZS IXIL exhaust. After that my sparks are almost white. I understand that engine is getting not enough fuel right now. I ask a motorcycle mechaniker and he told me to mount a dynojet. Can i "go around" it and just mount a bigger nozzles in my carburetors ? What size of them?

I was searching, but don't find anything 

Soryy about my english. I'll be greatful for any help.