guys I discovered how to make my
M2 LCI backfire (aka
"gunshot bang") in a
RELIABLE way.
the sound produced is exactly like the one captured by
andrewc89 video. Thanks for showing the correct rpm range sir
2nd gear, sport mode, just below 4000rpm, floor it to 5000rpm and let go.... bam
In my car, it only works in sport mode, not sport plus nor traction mode (haven't tried comfort or TC off).
I tried in sport plus many many times but I was getting only a muffled sound and sometimes a "fart".
Sport mode is the key 
PS:
For reference, here's the pic of my NBTevo version... no idea what ISTEP/Frimware I have
