Low rpm rattle

Hi guys, thanks for all your recent input regarding my tire issues.

On to my next issue....

I have an annoying rattle sound that comes from my 2006 330i. It's mostly noticeable when passing parked cars or in parking garages but I can hear it at low speeds also. It happens when the car is in motion only when the engine is spinning between 1000 and 2000 rpm. The noise cuts in and out sounds like a stick/leaf in a fan and seems to be coming from the rear portion of the car. It happens mostly when I accelerate moderately at low rpm in every gear except 1st especially going up hill. However I also noticed that it happens when cruising whilst in gear and also when cruising with the clutch in. It also sounds when the engine is in motion and I pulse the throttle a little but not when idling....

I have no idea what this could be and none of the symptoms seem to add up to nothing I've seen before.

Help!

I have a shudder in my 2007 328xi when I am going up hills at rpm's under 2k, related?

It's not a shudder as such. No effect on the performance. You cannot feel anything wrong through the controls but you can def hear a rough rattle. I've read that it is common on the 335i. Due to turbo waste gate but obviously not on mine