Backfiring thru your exhaust is ok, backfiring thru your intake/air filter is a NO GO!!
The intake plenum is plastic
look at what happens to cast aluminum intake plenums when you get a back fire!!
Pic of my intake plenum on my 350z after a nasty back fire...
It will fcuk your hood up too
Yes be concern if you hear backfire up front by the intake / filter area