you're refering to the ALS (anti lag system), basically when you close the throttle(in gearchanges mostly)instead of actually shutting the throttle butterfly, it keeps the butterfly open at full bore and cuts the ignition instead (allows the turbo to keep spinning) thus dumping a load of unburnt fuel into the exhaust, witch as a side effect goes boom and can whizz the turbo round even more. hence flames and popping
a backfire's pretty much the same thing, (fuel not burning in the chamber) but caused my many different things (closed throttle on hard overrun is usual for my motor)
and a misfire is usually just a glitchy ignition system etc. that causes the engine to miss a few beats every now and then, (sometimes resulting in a backfire)
hope that clears it up