Alex, it doesn't appear as if you have opened up the transmission case to see what you have going on. If you are in the US the restrictions on a 50cc Kymco were in the variator boss; not typically in the CDI until newer years. If your spreed exceeds 30mph your restrictions have been removed.
Now if you add an aftermarket, expansion chamber type of pipe you can expect an increase in acceleration and top speed - if you do the rest of the set up correctly. That is going to lighter rollers, and adding stronger clutch springs. Your top speed could be increased by 5mph give or take.
Remove your variator weights and weigh them on a scale. Have a set of weights .5 gm, and 1gm lighter than stock. Leave 3 stock in, and 3 of the .5 gm lighter - button it up and give it a test run. Lighten up on the rollers until you get the results you want. Don't bother if you do not change out the clutch springs, as it won't work out the way you want.
No one can tell you exactly what weight rollers to use as their are too many variables. You have to do the wrench work, testing and tuning.
A slight bump up in the main jet size MAY be needed, but depends on the pipe.
Open it up, and check it out. Good Luck.