Here is a very simple way to improve ignition system for internal combustion engine. All you need is a high voltage non-polar capacitor. I use 100 pF 40 kV Ceramic Capacitor. Just clamp that capacitor directly between spark plug electrodes. And that's it!
PS: you have to use resistorless spark plug.
Simple plasma ignition revisited: https://youtu.be/v_ECBmrUSyM