2013 isx15 cm2350 black oil like substance in Air Intake again

[GhostHauling]

2013 isx15 cm2350 demandated 50k ago and it through a injector solenoid driver cylinder 3 code awhile back one time and I’ve noticed intermittent power loss hardly noticeable until recently still no codes but truck struggles to pull hills empty now so Upon pulling valve cover to check my injector harness and change out injector 3 if I need to and i’ve discovered this black oily substance in my Aron take again I found it like eight months ago and I I thought it was because of turbo slobber since then the turbo has been turned up so to create a bit of boost at idle. What else could this oily substance be? And could this be the cause of my power loss? Also one of the first things I did was pull the fuel filter and put a new one on and cut open the old filter and I didn’t find anything in it.