If the idle is better with onboard ignition being too rich isn't the only cause. Low Nitro methane and a too cold plug will cause the same symptoms. In a 4 stroke, you want the hottest plug available. I use either the OC type F or the Enya #3. Actually I use the Enya in all of my glow engines. To quickly check the idle mixture, pinch off the fuel line while idling. If the engine speeds up it is too rich. If it dies quickly it's too lean. Very simple check. Another giveaway that you are using a too cold plug or too low nitro is if the engine slows considerably when you remove your glowdriver after starting.