i have the same sound as well.
the guy at work shop told me there isnt any leak. i think u just need use to it.
i decide change to injen intake and see if there is any different.
but i feel the car become slower after i put topspeed on.
am i feel wrong or it is normal.
the car doesnt have much response at low range.
also, the guy told me, maybe i need replace the cat and intake as well.
so, right now, i just try to use to it.