well yeah, the "pshhhh" of the BOV, but then the sound almost on top of that. Maybe it is a tire chirp, it kinda sounds like that, but it even makes that sound on the dyno:
http://www.wannafork.com/files/joel_546whp.wmv
this video is kinda big, a little over 12mb.
unless its also chirping on the dyno. Maybe it is, and I'm just a noob. I haven't seen too many videos of cars like this one, putting out that much power.
and yeah, i wish i had a 300, too. such beautiful cars, with the muscle to back it up.