Axle back (two mufflers) I think it sounds great. Perhaps just a little bit louder than I'd like on the highway, but lots of fun. I think I lost about 5mpg because I am constantly "playing it" with my right foot.

I will add photos soon.
http://www.youtube.com/watch?v=MB0bikX1xsw
BTW, I'm new here. Or I'm not and I just lost my old login. Anyway, got the G37coupe a couple months ago, after 7 years with a G35 coupe.