I've heard of others having this, where there's a fast knocking noise at idle, but only if it's in drive. Put it in park and it goes away. Should I be concerned.

Knocking? It is actual knocking/pinging or it is just valve clatter?

Valve clatter is normal for these engines, the valve train is a little noisy due to the timing chain and VVT-i.

Knocking is not normal though. I wonder if knocking is really what you are hearing though. Shifting an automatic into park should have no effect on this if it's actual knocking, unless it occurs when the engine is under load.

I say take it to the dealer. If it is actual knocking and they tell you to use higher octane, tell them to f-off and FIX the problem.

Are you due for an oil change? sometimes that will amplify this type of noise...

no, but mine putters since im misfiring

i actually had this problem on my 5 speed manual, i got an injen short ram intake and it doesnt do it anymore.

Knocking = bad

Take it in to the dealer and have it looked at under warranty

Well, I guess it's more like a ticking noise.

Mine has the same sort of thing, Iv thought I have read that its the fuel line.