Steve, as you've seen there's a learning curve involved when going gas. The DLE 20 is picky on it's carb settings, and to make that worse, the ones supplied with the 4.8-6v voltage modules throw a curve at you. That module has a single "step" that advances/retards the spark at about 2200 rpm. The newest engines are supposed to be coming with a 4.8-8.4v module that has a more progressive curve.

So to your questions, first that plug is unpredictable. Most scrap it right away or as soon as ANYTHING gets wierd. It's capable of so many different problems, that's just proven to be a good move.

The other problem is known as "high idle hang". That timing thing on the earlier DLE 20 modules just makes the problem harder to figure out - a perfect storm if you will? So 2 things to help you get through this. First, if the idle is set a little high, like at 2000 or so, getting the engine down through that "step" at 2200 can be a PIA. The cure is to set the idle lower, like 1800 or so. The second is about the low speed mixture. If it's a hair lean it's going to do exactly what you're describing. It's hot, and it's taking it's sweet time cooling down. You can hurry or eliminate that cool down with more fuel - a richer low speed mixture. It generally will not take much. When tuning that low speed adj, many go for a smooth even idle, and that's going to leave you lean every time. A 2 stroke has a lumpy, unsteady idle when right. Getting used to that concept part of getting used to gas.

-Al