mine pops on decel most times but never when the car is idling/stopped...
unless you had cams/rotational idle of some sort and even then its not a popping sound more clumpy idle

I wouldnt say it pops anywhere as loud as decel but it kinda just burps every now and then.

you might have a small misfire... something similar happened to my dad 100 series tank

this is what im trying to work out. I dont really have time to take it to a workshop cause of work so trying to figure it out by myself. I put new plugs in a month ago but didnt check the gap as they where like for like. Might pull them out and have a look at them.

would get the tune checked.