[Sankar]

First start with an air filter like the Uni or the K&N, upjet your carb. You will get a slight improvement in performance.

If you want more add a well designed expansion chamber to the setup. Again upjet your carb.

For more performance think about getting your RX ported from a reputed tuner. Increase the compression by milling the head. Again check and upjet the carb. You might have to use another expansion chamber which will match the new port setup. Your old expansion chamber might not work properly.

This is not the end but if you do upto this level you'll get good performance out of your RX. Bigger carbs and aftermarket CDIs can be thought of during later stages it's not needed at this stage, the stock CDI is good enough.