Exhaust leak is a fair point, although following checking the bearings I ran it with the exhaust off from the downpipe and it was still there.
I've done the hose trick which leads me to behind the bottom pulley. The only thing I can think of in behind there are idler bearings and the oil pump. Has anyone heard of an oil pump going?
I've also tried the screw driver and there is no 'solid' noise wherever I place it, which leads me to the thought of plastic. Haha, doesn't really narrow it down tho huh?
Perhaps I'll pull it back down to the cambelt again and try running it without the covers (carefully) and see if the hose can get me any closer to the origin.
I removed the windage tray when I checked the bearings and it was tight when I put it back on (and if the windage tray is in the sump, that piece of metal wasn't rattling either when I cleaned the sump out!
Also, how does one check the oilpump for condition?
Thanks again guys