I doubt PWM is the way to go. Multiple Strike Discharge takes advantage of the fact that most ignition circuits have a natural tendency to 'ring' after the first arc occurs and you can 'excite' the coil at that natural frequency for producing a few more arcs. There is a limit to how many times you may want to re-strike the arc. I think the natural resonance usually observed on an oscilloscope is between 25KHz and 100KHz and must be examined to find the 'sweet spot' for your circuit to be most beneficial. You will know if you got it right as the sparkplug electrode wear increases about 5:1 and horsepower gain is 2% to 5%. B.T.W., 'Indexing' your sparkplugs (adjusting the seated position so the 'L' shaped electrode is sitting properly between the valves) could add another .1% to .5% to your power.