I have an 07’. A little different set up but I have oil residue where all the rubber connection are and that’s normal. Maybe there’s a gasket inside where the residue is that is broken?
The 2008 has closed crankcase ventilation, so it's common to find oil residue throughout this piping. If you feel like the amount of residue is excessive, you can add the crankcase filter and breather cap from a 2011 and later truck.