fuel leaking and dont know how to stop it! help!!!!!

[LiftedStroker05]

ok, so i just bought this 2005 f250 6.0 has 95k on her...
has air dog fp150 fuel system
6" roughh country lift kit
k&n ait intake
ARP studs, ect.
anyways, i was filling it up last night and i started hearing this slow leaking sound. so i crawed up underneath and im getting a leak from some mystery line going from the high pressure fuel pump to the tank. it has one of those quick conect tips.. heres where im stumped... EVERTHING IS PLUGGED IN ON THE HIGH PRESSURE FUEL PUMP. there is nothing for this mystery line to plug into. here is a short video of what it looks like
please help guys ;(

Air dog fuel problem - YouTube

Air dog fuel problem - YouTube

[mustangmike6996]

can you trace (follow) the line back to its point of origin? im fairly new to the diesel world so i couldnt tell you what that line actually is.