I'm interested to see where this goes... there has to be something going on here.
Flames shooting from the exhaust system is not typical. If one model did that, there would be a million threads where owners of other models would show up asking how to replicate the "afterburners", etc.
The fact that we haven't seen those threads is pretty good evidence that this is unusual. Try calling BMW directly. Either way, please let us know what you find!