I show under truck 3 fuel lines. Which is what and why?I assume two returns and 1 feed? Also doesn't the CP3, fuel rail and injectors return fuel to tank?

They say a photo is worth 1000 words... I only recall 2 on mine, the 3rd could be a brake line??The CP3 and injector return lines merge into one at the fuel filter housing.

I see two alumnium gray lines and one black. I assumr your right and black one is brake line.Is there a drawing diagram for how cooland flows? Like cut out or diagram? Same with return fuel line, cut oit or drawing?

The fuel supply line on my buddies '10 was black. Really a photo would be huge.

Here you go

It must be a 4th gen thing with the black fuel lines.

Yours looks just like mine. Top is supply, middle is return, bottom (black) is brake.

Do you know how the coolant flows through a 6.7?

Since it's based on the same block as the 5.9 I would assume (here we go) that it's just like this...

What are you trying to do?