N-14 chatters and knocks

I have a 95 N-14 460E Celect (not plus) I had it overhauled back in February. I have approx. 40k miles on the rebuild. Replaced the heads kept the injectors. I have been getting a chattering noise when I accelerate and at idle since the rebuild. The noise kept getting worse. I thought maybe it was the overhead so I went in and had the overhead set. It did no good. Drove it for 15k and it still chattered but I noticed a slight knock. It only knocks when the turbo boost is between 10-20 psi. When it starts knocking if I accelerate the knock will go away. Let back off and as the boost drops it knocks again between 10-20psi and will continue to knock. It loves to do it in top gear around 65mph when the turbo hits 10psi. The higher the RPM's the faster the knock. I took it in and had a Cummins Tech ride with me. He thought it was injectors so I dropped injectors in it and re-ran the overhead. It did me no good. I had another Tech ride with me today and he don't have a clue what's going on with it. Any of you good helpful folks have a clue on what might be going on with my old Cummins?
The knock is loud and it still chatters at idle, both seem to be getting louder with time. Please HELP!

 

Thanks VisionLogistics, however my engine does not have EGR and the turbo is also pre-waste gate. The knocking sound sounds almost internal in the engine. I don't think it is turbo related because of the chatter at idle. I could be wrong though.

 

It spins free and starts right up no smoke, no missing. Sounds like the classic n-14 other than the chatter at idle and knock going down the highway. Tech thinks the chatter is coming from around the accessory drive area but wasn't to sure.
Do you think a bad air compressor could cause knocking? I had my air compressor replaced almost a year ago and now it pushing lots of oil out the dryer. The intake to the compressor is dry no oil coming in. I'm not sure if boost pressure variations could cause a bad air compressor to knock. Just a thought since it's intake comes off the intake manifold. I gotta get that fixed while its still under warranty.