Lets go over what's actually going on:
Decelration popping is the result of a hot spot in the exhaust igniting the mixture in the pipe. You can eliminate it in two ways with the tune: Remove a ton of fuel or Add a ton of fuel. Either method, you'll still likely get a single pop during decel when riding in a spirited manner if you rev it high like 5500+ and close the throttle and allow it come down, the extra fuel from that closure at high RPM is a lot of fuel and will ignite at some point. I use complete fuel cut at high RPM with closed throttle like that, and I still get a big single pop right around 3000 RPM coming down in gear throttle closed.
Each method has its' pros and cons:
Leaning it out - Doesn't waste fuel, doesn't smell of fuel, eliminates all of the popping, usually leads to a rough on/off throttle transition.
Richening it up - Wastes a ton of fuel, smells like gas, eliminates most of the popping but you may spit flames, usually smooths the on/off throttle transition.
Shuffling tunes isn't going to fix anything if there's a vacuum leak allowing extra air in or an exhaust leak allowing extra air in. Both will absolutely cause excessive exhaust popping and rough running at low RPM and low Throttle, as you've stated it has. Tune doesn't matter in either case, you'll have the same symptoms.
But I'm no expert, still trying to get to grips with the basic mapping logic of the bike and have yet to try one of Hans0's maps with differing F L switch and L table setup from the triumph tors map (20776)...I need a new rear tyre before going out to test any more lol
