Hey guys, need a hand locating the source of a rattling noise thats developed in the engine bay of the car over the last couple of weeks. 
 
Something seems to be coming loose and rattlingaround and it seems to be getting worse as it was barely there a couple of weeks back to the point that I thought I was hearing things. However it is unmistakably there now and bad enough for passengers to ask what the noise is!
 
I first heard the noise when driving through the mountains, when I let up off the gas from relatively high rev's I would hear this noise that I thought was just a burbling sound from the intake. But as its progressed it can now be heard on start up too. Once the car is accelerating the noise stops, but if I let up it can be heard again. It seems to be louder when the car is not level with the front up or down but can still be heard at any angle and its annoyingly inconsistent.
 
The noise/rattle is there with the clutch in or out, and in gear or neutral so I don't think its the transmission. I think the reason it stops when accelerating is that only the really low rev's resonate with it and cause it to vibrate against some part of the car. Its clearly audible in the cabin but hard to hear with the engine lid up over the normal engine noises unless you stick your head under the car!
 
Any idea's on what could possibly be coming loose or areas of the engine bay I should be looking?
 
Any help is appreciated guys, I've got a club run next weekend that I'd like to have this sorted by as I don't really want to push the car with some random piece of the engine potentially about to fall off!!

Exhaust manifold or turbo downpipe heat shields could do this. Check the bolts that secure them.
 
Even a tiny exhaust leak can sometimes sound a bit like a rattle. 

Might be a cracked exhaust bracket. Have a check under the car, a bracket might be cracked in two somewhere.

+1 if it is an NA with the stock exhaust.
There is a  bracket welded to the end of the pipe going into the cat that links to the muffler.  The weld often cracks and can rattle.

I had the same issue. I found that my pulley tensioner below the cam gears was loose. Or broken I can't remember. Give that a check

Thanks, for all the help guys, I finally got the time to have a good look from underneath the car and found that 2 of the engine mounts were stuffed! This lowered the engine about 12mm causing the exhaust to rattle, now that new mounts are in and the engine is back up and everything has enough clearance the noise is gone :)