Never hear the noise at idle, never under load, only when the engine is free revving around 2000 RPM, either in neutral/park or that few seconds between shifts. Even though the exhaust is starting to rattle inside I'm just not sure that its the noise I'm hearing up front. [/quote]

So now what? In the end the exhaust was an easy fix but like i said before I just don't see how that Diesel sound could travel up the pipes and into the engine...

One thing i did notice is that the engine has to be hot to rattle. I still think it sounds like valve train but could that come and go under load? Could the injectors make loud chatter?