Here is my diagnostic question/challenge.07 LR3 V8. I hear a noticeable rattle or chatter under higher rpm acceleration that is proportional to engine RPM. No unusual noise at idle and no noise when keeping the rpm low. If I have the truck in neutral and rev the engine there is no noise. Along with the noise there is a stinky gas smell from exhaust (both banks) and perhaps somewhere else but I can't tell. I have a the following codes;(Attached) Where should I start looking? I tried hunting for an intake manifold leak with a propane torch to no avail..

 

If the "rattle" is worse at high RPM and underload and with those fault codes along with the "smell" I would look at the exhaust manifolds.
I have had bolts that needed tightening up to resolve a leak that caused a similar noise.

General Disclaimer: I might be wrong

Jeff