I recently installed an AFE Cat Back Exhaust on my Xterra......but I must be getting old because the drone at a certain RPM range ((2300-2700) got to me, causing me to move back toward an OEM style system.
It's only got about 500 miles on the system. I also had a Vibrant Ultra Quiet Resonator installed after the muffler, which helped a little with the drone and deepened the exhaust note.
I did see both performance and MPG gains with it on the Xterra.
It's in great condition. I'll add pics soon. Looking for $300 (OBO) for the system. Also, with the bulkiness of the parts of the exhaust system it will be local pick up only (Omaha, NE). I am also willing to meet you within a reasonable range of Omaha.