On my bike, especially around 5k, it will pop and burble. At night this can be seen as small flame peeking out from the tip of the slip on. I can make it do it more if I open the throttle 1-5 ish % on decel.I have not but a wideband o2 sensor in the exhaust (have innovate wideband for the supra), but reading the plugs shows my bike always runs rich. I am not concerned about a little pop or burble on decel, I actually like the iconic carb sound

My bike appears to be tuned to run with the slip on removed (by po) from reading plugs. With the slip on installed it runs rich, definate black on the plugs. With the slip on removed it runs barely rich, with signs of carbon on the plugs looking almost perfect.

 

So it turns out the carbs had an air leak.

I swapped the carbs last week with my spare set(saves having the bike off the road while I do a carb clean)and after a close inspection of the intake boots one of them had a small split/crack in it. So I replaced all 4 boots and problem solved.

It still has a nice crackle on decel which I like, but no splutter or loud popping.