I have borla headers, stock cats and borla cat-back on my 02 OBS and it's loud enough. I don't know what I would do if I had a high flow cat or even no cats. The borla truly, IMO, gives our scoobies the boxer sound. The way it idles then when you open it up sounds bad a$$!
I'll see if I can get some recording equipment so you can hear what is sounds like.....it's very nice!