I have an Agility 50 and now get around 48-52mph top speed, on the clock, was 31mph stock.
I did my cdi then my variator boss and put in a bigger main jet, this gave me around a 10-12mph gain. Then I fitted a race variator, off ebay, and lighter rollers, got another 8-10mph.
Am pretty happy with it now but would like a little more uphill power so this weekend im putting in a 1000rpm torque/contra spring into my clutch. This should hopefully keep my gearing better for hills etc.
If its not fully derestricted do that 1st, then go for a race variator and lighter rollers, big improvement.