[trularin]

Dave, Sounds like you might have a too lean condition.

I can not remember if you have a carb or FI, but what you can do is sweeten the mixture at the idle screws and see if the problem goes away.

It is common if you use the engine as a braking assistant and the engine revs are high enough to need more fule to sustain them. Yet your foot is completely off the pedal.

Simple way to check may be to give a little pedal as you slow down and see if the popping stops.

Just a thought. Are you still drinking with the cows?