If you hold the exact right RPM you will get a little drone, haven't noticed any rasp. The hiss is interesting though, I even like it as it's not that loud, just noticeable. There is only one problem with this system, you will want to drive everywhere just to keep hearing it.
Man does it sound awesome. It makes you want to find a closed section of twisty road, install a roll cage, throw a helmet on, and go ballz out until something blows.