Follow back those lines that go from injector to injector, you'll find it at the back of the motor. I'm not sure precisely how it routes but it goes back to the tank selector valve.
1992 F250 XLT 4x4 Super Cab 7.3 IDI E40D 3.55 ATS 088 4"R.C 360k
1982 MBZ 300SD W126 California model w/Sunroof, no EGR
1997 Audi A8 Quattro 225k Warm/Cold packages