2004 maxima rattles on acceleration

I have a 2004 maxima, I have noticed a rattling/buzzing noise when i accelerate from a stop or pulling a hill usually around 1500-2500 rpms, never does it while idling. I would think if it was a timing chain problem it would do it all the time while running. Anyone have any ideas as to what it could be?

could be as simple as loose exhaust heat shields.common problem