Oil Pump

[kmk]

I recently tackled a similar issue, rather time consuming and difficult to test. Make sure you are with a good shop, willing to diagnose rather than through parts at it. Use uv dye and a high pressure pump. If you dont have loss of prime or misfires, most likely you are looking at injector orings(top ones) or cracked head, in my case was the head, the crack was so small that it didnt show until we pressurized it to over 90 psi-you can use the injector tester plate for the actuators to isolate the problem. If your oil is black just run the engine with dye from a bucket.