The popping is caused by the fuel boiling in the distributor ring. At low power setting, the fluid flow is so small that the kero gets the cance to heat up to boiling temps. When the air bubbles exit through the needles, they cause a slight flame surge, and when it comes back on line it makes the pop. Throttleing down even more, you will probably start to see rpm vary, all the way to a flameout...
Solution is either to use high grade diesel fuel (higher boiling point), or modify your injector ring to a slightly larger diameter to get it away from the heat and into the cooling airstream...
Regards
Hank