40k Later...
I had the same problem with my 408W and installed an A/C idle solenoid to hold the idle up when running and let it close the throttle completely when the ignition is turned off!!
It dies instantly now but I have since discovered that my electric fan was the culprit!! After the ignition is turned off the fan winds down and generates enough current to keep the ignition hot for a second or two.....VOILA....DIESELING??
You might want to check this out as well before you make too many changes??
Good Luck!!
Coosawjack
