I'd say a good exhaust makes power without being loud.Any good exhaust that makes power will be loud. I wish Nmotion would make a pipe for the xx because thats what I had on my yfz450 and it was REALLY LOUD but it ripped.
In SoCal you can contact Daniel (DL700) at http://www.highdesertdyno.com/Looks like I need to get a Sparks or a Barker. Do you know of a shop in SoCal that can do some engine work and tune it? I have emailed Trinity Racing 3 times and they have never wrote back and when I called them for pricing they told me they would call back and never did.