[Ripsco]

So this just started today on my way home from work. Under medium acceleration I hear this strange rattling sound coming from the engine bay. Under light or hard acceleration I do not hear the sound. Only on medium acceleration and it does not happen all the time either. The car still pulls and drives normal. I hate to say it but it almost sounds like VTEC kicking in kind of sound. Could it be maybe my UICP banging against something or perhaps a heat shield? Any input is greatly appreciated.

Thanks