Its just running rich? ie. the R&R that normally occures with std ecu? 12PSI? on std turbo everyday? damm
My car backfired heaps when I did a few more mods to it and uped the boost. It would backfire every gear change, every downshift, I was even able to make it backfire on demand. Off throtle and on throtle etc..
Sometimes it would backfire by itself 4times in a row! "ZOOOM POP POP POOOP POP"
You shouldnt have anything to worry about, just means car uses more fuel, and the cat might be rooted lol