Strange Noise

[JMO]

Hey guys,

There is strange noise coming from my car. It sounds like 'cluk cluk' and can be heard when idling (very softly) and gets faster and louder as you rev the engine - stationary or moving. I've tried to pinpoint it using a screw driver as a stethoscope but can find exactly where its coming from. I think its coming from under the car but it could be coming from somewhere in the engine bay but masked by other noises. I've listened to the injectors and coil pack and its not the noise that I'm hearing and I'm pretty certain it's none of the pulleys at the front.

I've heard other AU's that have a similar clicking sound as they drive past but I'm not sure if its the same.

Anyone got any ideas on what it could be?