CDI will not help you much.
It is logical that with higher gearing, you won't reach the same RPMs. With higher gearing, it's harder for the engine to spin up high. If you want super high RPMs, gear low. You won't go very fast, but you'll accelerate quickly, and really whine up there, because the engine has to turn more RPMs to get the same speed.
Blah, I'm drunk. Experiment with your timing more than simply running it at full advance. Timing is really a touchy beast, and the power is really in the points. Honestly, correct timing changes EVERYTHING. But yeah, you should be running at least 16x45, if not 17x45. The 50cc TCCD is notorious for shitty low end. You need to tune your clutch to at least TRY to compensate.
Bullet pipe is not ideal.