Interesting electrical problem

Ahh interesting idea. Any idea what the correct length/gap would be for a happy time engine?

Do you know if the current spark plugs /boots supplied have suppresors in them?

No I don't. I use a Robin Subaru.

Suppressors can be in the plug, in the connector to the plug or the secondary wire itself.

I would use any resistor plug handy that is the correct length just to run it awhile to see if it helps...then look for the correct plug, a plug chart will show it.
Which would be the best. I have just ordered a plug boot with a supressor in it as its cheap and i can see if it works.

Would a resistor plug work better?

They are about the same. Some ppl use both when the car radio is picking up the signal of the ignition secondary.
I have the same problem with an electronic speedometer. Works fine as long as the engine is not running. I'll have to try that resistor plug idea. Thanks.