What color was the cdi? One way to check if your bike is limited is rev it up on the center stand and if it revs out your good, if it goes brap brap brap your limited. If the cdi was brown you should have that wire, it's coming out of the base of the cdi away from the other wires. The people 50 can bury the Speedo stock if its running good. You can upgrade the cylinder to 70cc with editing else stock, the early p50 have a 17mm carb stock but you would get more power by going with a 19mm carb and cylinder kit. How you build your bike highly depends on if you are looking for torque or speed. For top speed you will need to do A LOT more. If you're happy with a solid 50 but with loads of torque, I.e. Flying uphill, then di just a kit and call it good. Won't even hardly need to change your jetting.