When I talked to the guy at Spintech, he mentioned the side exit ones like mine sound different to all thier other ones and was just a unique note. That along with my X pipe actually makes them real quiet at idle, and perfect (to me) when you are getting on it.
I am nearly done building most of the car so will get some street time in shortly, only been up and down the street a little bit so far (finally got the hood on it tonight
)