Metallic knock?

[VQ magic]

It usually happens when I just take a turn and the car is in 2nd gear, I hear this metallic knock coming from the front of the car. It also happens sometimes when I go up a hill. Usually only happens when its around or below freezing. Any idea's? I do feel a slight lost of acceleration as well as a noticable knock/gargle/clank so I think it might be my coil packs. Can't be the heat shield covering the downpipe because it was removed along with the factory unit.