Determine if the oil is coming from one cylinder or multiple cylinders.
If it is coming out of a particular cylinder, check the valve guide seals for damage and check the valve stem and guide for wear.
If it is coming from all six cylinders, look in the air inlet and CAC pipes for oil from the compressor side of the turbo.
Check pressure output of the APT air solenoid.
If the air pressure output is in spec, change the APT. Refer to "4.3.1 Removal of Axial Power Turbine"
in the “Air Intake System” chapter of the EPA07 DD15 Workshop Manual
(DDC-SVC-MAN-0002).
If the air pressure is out of spec, change the air solenoid