Speedy, 3W and DA do not run resistors in their plug caps and run CM6 plugs as well. I had never seen this until the Chinese engines started showing up. However I do not think that adding the resistor is going to hurt anything. Once you source the wire you may want to just order up a couple DLE cap kits, they come with the resistors and instructions. The Reichmouth ( I know that is spelled wrong ) ignition that comes with the D&B engines is really well made and gave me no issues during hundreds of flights. In fact it was the most maintenance free engine I have ever owned.