weird engine sound at idle
 

So basically, my 8's engine has been making a weird noise, robotic like. Its a 2007, manual transmission and it only happens at idle, it goes off after accelerating or increasing the rpms a bit on neutral.

It started happening a few months ago, but it wasnt so often. Now its happening like everyday and its getting a bit louder. Im attaching a video so you guys can hear it, you might think its the usual engine sound but its not. It has stock air intake, with the modded box and a k&n air filter element, nothing more, and it happened for the first before before even changing the air filter.

http://www.youtube.com/watch?v=KHjeBhH0bYI

Any ideas? From searching i just came up with stuff like heat shield or engine mount broken, but these stated that the sound was at high rpms or not at idle like mine. Its kind of annoying because it can be heard inside the car even with the radio on, and its quite loud on the outside.

Can you at least tell if its coming from under the car or the engine bay?
My first guess is something under the car tapping such as the exhaust hanger or the channel guides for the fuel and brake lines came loose.
The exhaust hanger on my AP cat-back used to tap against the diff... until I cut a little bit off.

If it sounds like its under the car, put the car up on jack stands, climb underneath with the car running, and WEARING GLOVES start feeling/listening for the sound.
Move sections of the exhaust side to side and see if the noise changes or stops.

i get a similar sound when under load at 3.5k -4k rpm.

I checked the exhaust hanger it does not appear to be hitting, checked heatshield above exhaust doesnt seem to be hitting.

It has about half a cm gap between the rear cross member and the cat, could this be the reason?

Regards
Jason

In my case, this sound was coming from... well the hood hinge/latch, whatever its name is ._. The hood closed perfectly but it seemed that below 1k rpm something in there vibrated and caused the sound. I just sprayed a shitload of wd40 and now i havent heard it since (2 weeks+)