2006 Eclipse: Noise during accleration

I have a 2006 Eclipse GS, 5 speed manual, nothing crazy or odd modifications, factory spec'd.

During acceleration I hear a 'rattle' between 2500 and 3000 RPM. Rattle is the best word I can think of, sounds almost like, metal ball bearings inside a tin can. Pinging/rattle noise.

If I don't pause and continue to accelerate it goes away right at (just before) 3000 rpm.

I don't have a clue where to start or what to look at so any help/information would be great!