I was researching the VQ engine and your engine sounds like it needs valvetrain / head work on it.
Here are some video's from teh VQ35DE engine V6 and should help with diagnosing the sounds.
YouTube - Knocking on Nissan Maxima (1)
YouTube - Knocking on Nissan Maxima (2)
YouTube - Knock on Nissan Maxima (3)
KNOCKING REVEALED
YouTube - Knocking revealed on Nissan Maxima
Rocker arm damage or something of that sort
REVING ROCKER ARMS
Urgent Help need valvetrain chatter and tapping...Maybe TDI?? - G35Driver