That sounds like what my car does with the CAI and brenspeed tune. I've been trying to figure it ouut. I posted about this last night. What's your experience with this?
Fortunately / Unfortunately, I have a lot of experience with this. However, all of mine came after supercharging. 1st time happened after getting my ride detailed for a car show. When the detailers were cleaning the engine bay, they flooded my Diablosport MAFia with water. Would start only to die. Only a hunch had us pull the MAFia apart...and water came pouring out. So, let it dry, put it back together, started driving away, and all I'm getting is gun shot-like noises on rpm and speed decel. After a while it started getting worse, to include all of the symptoms in my OP. I got with a mechanic muddy of mine and we started going through everything that could possibly cause some detonation, which is one of the main reasons for back-firing exhaust. Come to find out, one of my spark plugs unwound itself in the process. Tightened the plug back up and car was cured...until...
2nd time this happened was after a track event late summer last year. After I got home, same symptoms showed up and this time I knew exactly what it was. High revs, high speeds, heel-toeing, high temps. I knew it unwound my plugs. And what was worse, I started getting symptoms BAD the night before heading back to the track. I had the wrong tools to screw my plugs back in (I'm running HT0's because I'm supercharged), so I headed to the only shop that was open at 8pm on a Friday night: Pep Boys. Because for some reason I got it like that, I was able to use one of their bays, use brand new tools right off their shelf, and screw my plugs back in. All it cost me was some "guy time" talking junk about cars, life and other
with the fellas who work there. Pretty awesome. Turns out one of my plugs unscrewed itself almost all the way out, while another plug only required a about 6 turns to get it tight again. Tightened them back up, headed to the track, and I've been good ever since (knocking on wood).
Long story short, you might want to check your plugs first.
I can't remember the size socket for stock plugs, so maybe someone else can chime in.