+1 for that noise in the 3-4 K rev range.
not always there, but did improve a lot after i serviced the auto.
im convinced that its a slipping clutch pack or simular in the auto.
mine no longer does it unless i really load it up, like 4/5 people in it or a full tank and a heap of gear in the back...
the weird thing is, when the sound appears, giving it more jandel (thong for you aussies), makes it go away. maybe a bit more heat makes it lock up quicker?
mine has the stock turbo, but has had a kakimoto R system fitted, and is running around 14 psi.