yes cdi is fully free after you cut the pinky wires , i have also 4t so no boy you cant get more speed with 5.5gr rollers because of high rpm the lower the gram of rollers the higher the rpm
im having polini variator and cdi trick and dont get more than 65km/h even on 6.9gr rollers
kymco is a known brand for restricting their scooters badly
im thinking to move to a bigger carb that makes a significant change at a fair price
there are some kinda projects to make s8 faster but it costs a lot i dont think you have the right scooter if you're a speed freak :p