Strange rattling noise from under the bonnet between 65km/h & 55km/h

[ADM]

Hello all, My AWD has done 134,000kms and in the last week or so it has developed a rattling noise primarily when decelerating between 65km/h and 55km/h.
It almost sounds like keys rattling or even chain rattling, I've checked for loose bolts/fallen bolts & fittings but all came up ok. Seems to be coming from the passenger side. It does it a little on acceleration if the throttle is feathered between the speed ranges indicated. It's not particularly loud. To hear it properly, the windows need to be down and the sound reinforced from a nearly by wall or fence but it can still be heard in the cabin with the windows up but you really have to listen for it.
The driveline isn't shuddering or vibrating abnormally, it feels as smooth as the day I bought it actually and there are no leaks apart from the steering rack (which will be replaced upon getting my tax return & the steering doesn't make any unusual noises). & before I get any "take it to a mechanic" type answers, I'm asking as funds are very tight at the moment as I've just been awarded a substantial paydrop and I don't have $90 > to throw at my mechanic every time I require something investigated.
Anyone familiar with this type of sound? Thanks in advance.

[ADM]

Problem found, was a loose metal boot that acts as a dust cover for the tail shaft where it connects to the front diff. It's a press on type that is secured by tapping it back on with a mallet. Yet another problem/bug resolved since having the new motor fitted :-s