Might sound stupid but i've had customers come in and say they have a strange noise under the hood and it turned out to be the heat shield.
don't no if it's any help or if that's even your prob.
anyway good luck.

Well I'm back with no good news. I have removed all the heat shields that were left and changed my oil to a heavier oil and the noise is still there. I can now hear it at light throttle when warm. Now that the colder weather has set in if I start driving on a cold motor it sounds like a Cat diesel. Warming it up helps lots in reducing the noise but doesn't eliminate it. I noticed this morning when I started it for warmup that it puked out some blue smoke then cleared up so it looks like the head is starting to go also. Why do big things always break right before xmas.