Over the past few months, I've noticed a leak directly under the rear fuel filter under the truck. The spot grew worse with time and seemed to be exacerbated by decreasing temps. I researched this forum and found some threads describing similar symptoms that I was noticing. It seemed most of the results of the existing threads pointed to cracked housings or ended up with a costly dealer bill with some users stating that fuel leaks weren't covered by the warranty.

I actually found this suggestion on the "Nissan Titan XD Cummins modified" page. It took me a couple hours of effort, but the repair was really quite simple. A little messy with all the diesel fuel residue in the area, but totally worth it.

The three blue o-rings found on the white plastic tee in these pictures were the culprit. The two larger ones were clearly aged and misshaped. Now there is no more leak. All I did was buy an o-ring kit from harbor freight. I thought I'd share my resolution to hopefully save someone else the pain of costly dealer bills.