This may seem really silly, but check all your o2 sensors on your exuast. My d2 was making a clattering noise under acceleration, and i could not locate it. I ended up sometime down the road having to change my front drive shaft and while under the truck I accidently knocked the o2 with a wrench and saw that it was loose. I tightened all of them up and sure enough clattering sound was gone and now she purrs like a kitten...I mean lion.

One post above, I identified the source of the problem... Bad Exhaust Manifold Gasket...