the injector pump is at the front of the valley between the heads, not too far from the fuel filter (or at least where mine was on my 89 f250) but fuel would not be going from the valley to the passanger steering parts. if your looking at your motor from the front look directly in the middle of the intake towards the front. the injector pump is the item there at the very front of the valley (should have a plug or 2 connected to it since yours is a 99) that has a bunch of fuel lines coming out of it (metal lines). each line runs from the injector pump to the injector at each cylinder. check the connections at each spot (where the line connects to the injectors, at the injector pump, at the fuel filter) and you'll see it.
i had a leak on the water seperator at the base of my fuel filter (sitting at the front of the motor just outside of the passanger side cylinder head) that was doing a similar thing.
that tube on the passanger side would likely be from your ac system to let the condensation drain out. diesel fuel systems do not have an overflow that lets it drain out (like older gasoline vehicles do), instead it sends the extra fuel back to the tank.
once you have found the leak you need to bleed the fuel system to get rid of the air, otherwise the truck will stall out until all the air is gone from the line (which if you dont bleed it could take months). bleeding the line is simple. disconnect the fuel line that goes from the fuel filter to the injection pump (disconnect at the pump if you can) and turn the ignition key to on (but dont crank the starter yet). turn the switch off after you have a steady stream of fuel flowing out the line and reconnect the line. crank the truck (will take longer than normal) and you should be done.
