If you have an
oil cooler or remote filter. I would pull the lines and see if there is any metal in them. There is a light you can shine that makes powdered metal show up. I cannot remember if it is a black light or what it was. If there is metal out in these, you know it's all through the engine. Especially if there is metal in the line coming out of the filter. You can clean lines, but an
oil cooler is hard to prove you got it clean.
If your not going to pull it apart to clean it, I would at least do this. Clean everything up top under both valve covers. Sounds like the intake is already off so clean everything there too. Then drain the
oil. Then pour kerosene over all the surfaces up top and let it run out the drain. It would be interesting to let the Kerosene drain through a clean white cloth to inspect for powdered metal. A gallon or two should do the trick. Let it drip dry. Then pour a couple quarts of oil and let it flush all the kerosene out the drain.
Replace filter and put cheap oil in it. Idle it a 5 minutes, then replace filter and oil again.