[unicoladron]

could be loose nuts/washers on your exhaust manifold. the mani-to-turbo flange also is a common place for nuts to "back out" if you didn't use the locking tabs AND if you didn't bolt your downpipe to your tranny.

also, my brakelines used to tap eachother in the engine bay which is annoying as shit. do you still have any heat shields on your exhaust mani? heatshields always rattle.

but really, just get in the bay and just move stuff around, ya never know you might get lucky.