I'm not so sure about the evo, but on most vehicles that I have seen on a dyno - the popping on decel or between shifts coincides with a lean condition. Intuition would tell us that its caused by a rich condition - unburned fuel igniting.
The reason the fuel is not igniting is because the fuel system has cut back fuel delivery when the user has signaled "let off the gas", but the engine is still spinning at high RPMs and is pulling a lot of air through with not enough fuel to ignite, thus creating a lean condition with unburned fuel coming out. The unburned fuel swirls around and if enough swirls together on its way out, it can ignite from heat.

Keep your eye on the dyno next time, I bet the af ratio is up higher (lean) when you hear popping. It has been any time I watch my stuff getting tuned.

If you REALLY want to make a good bang, get the car revving high (4000+ rpm), leave it in gear as its slowing down, and turn the key off for a second then turn it back to 'on' .. lol you might blow your muffler up though. I used to do this on some beater cars / motorcycles and it sounds like a damn shotgun going off. But I have heard of guys exploding their muffler.

 

hahah am gonna try this but will it hurt the car and why will i might and blow the muffler off

 

Blowing the muffler off is an entirely real possibility, yes. But I doubt it would happen.