Gray green substance under oil cap - Cummins ISX15

[SupVit]

yes, the emission system is working, not deleted. I take good care of the system, do not allow idling for a long time, DEF is always almost a full tank. Truck never asked for regeneration, always does it on the road.
Summer 2019 Volvo+Cummins dealer tested the fuel system on the road and in the bay, changed the operation of the injectors, the amount of fuel. Said the computer shows no problem.
Nov 2019. A private shop can fix everything, smart experienced mechanic. But, unfortunately, a new employee worked with my problem. Decided to change the compressor, I immediately agreed (I was a very young owner :))). Ride around the area, no knocks. But nothing has changed when you pull the trailer and the load.
Jan 2020 Rush center, useless guys. They found driveshaft timing, windshield brades worn out (I bought them 2 weeks before :))), bad buttons on the steering wheel and bad a/c dryer.
And my friends said me at that moment to wait little bit because problem has just begun to appear and I will spend a lot of money looking for it.