That's definitely custom. Someone probably had an air compressor hooked up in the rear or something to that nature. Where does the other end of the hose go?
Also what is that thing next to it? That's also got to be custom installed, I've never seen anything like it.
Did you buy a WJ that someone already built up some?
99' WJ, 2.5" Rusty's, Bilstein 5100's, JKS TrackBar, Moog SuperTrailBoss
"With enough fabbing, time & $, it's certainly possible.
That being said, it's like boinkin' your sister...just because you can, doesn't mean you should." - Double E