Update: So my street race has just over a thousand miles on it and it definitely calmed down a bit. I know some of it is just the fact that I've gotten used to it but others have also commented that car is a little quieter than when the system was brand new.
I really love the way it sounds...
Just installed my street race today... Wow. Very loud. I'll let it break in before I decide if I need to tone it down. However, it is nice that the car finally has some sound to it!