i have a clunking sound too... its a very light and not too deep.
similar conditions to yours, mine can only be heard during slow turns or slowly applything the
throttle.
BUT - i think i have a standard LSD, i have spoken to my mates and they have heard it too..
they reckon its NOT the diff, and more possibly the exhaust (stock) which may have worked
itself loose or something.
I notice no difference in how the car handles however... does this sound like your problem?
i'd be interested to hear what others think?