I get almost the same thing. The longer the car is at idle the more it will pop on decel. I know it's running rich because my wideband is telling me 11.5 where I should be getting around 13. I need some tuning but I also got a new O2 sensor. The bigger prob is that I think it is part of and idle or low RPM stall out issue I haven't yet resolved. In general though, I wonder if it's just the nature of a rotary?