318i Auto noisey driveline

[FlashBastd]

Hi, I am having a few probs with my driveline. At motorway speeds there is a rumble from the back, which disappears under load, and when the throttle is closed. There is also an occasional knock from underneath - this had been masked by an exhaust that didn't fit well, but now the exhaust has been refitted I don't think it can be that, it is also not as loud as the exhaust banging.

Anyone any ideas?

Finally I have a nasty rattle from my downpipe, anyone know what that might be? It sounds to be ahead of the cat.

Thanks!!