Are you talking about the Blitz Supersound cause I that doesn't sound like an RSX and when I heard it on one before it sounded like crap. the best one I've heard even though this sound clip isn't an RSX it sounded just like this on the RSX I heard it on before. Its the Greddy Type-S. Kinda the 2F2F Skyline sound.
I think it is Blitz, but I am not sure. I got the wave file about 8 months ago and did some sound manipulation to get the sound more distinct.
Not every BOV sounds like that. When you get a BOV, you should ask what kind of noise it produces. I know of an Integra running almost 20 psi and he has a fairly quiet BOV. On the other hand, I know an eclipse (3rd Gen) running only 8-9 psi who's BOV sounds like a train whistle.