Ticking/knocking noise at high rpms under load

So I recently had the same issue with a rattle only under load only at operating temps pretty much same exact issue you describe I have a volvo with a cat 3406e I took it to all sorts of mechanics and a cat dealer to try and diagnose it no one could figure it out I drove it until it broke on me something let go inside the head possibly a valve I'm not sure yet but this week coming up I'll pull the head and let you know just my 2 cents is don't waste your money trying to change this and that I'm 10k in the hole from changing injectors twice to air compressor and everything in between I wish I just kept driving and saved my money I was trying to prevent a breakdown on the road and a hearty Towing bill but my luck didn't work out

 

Did you ever figure out what caused this? We're in the shop right now for the exact problem.