Be a tad wary when trying to compare EGT's with other vehicles.
There are HEAPS of variables that will give different readings for different vehicles.
Someone else may simply have their EGT probe an inch or two further away from the turbo for example.
Your temps don't sound all that far off the mark really... what is your fuel consumption like?
Oh and of the 3 "rattly" Cats I've seen it has been the heat shield. Try temporarily jamming something between the Cat and Shield and see if that fixes it... if so then you can sort out a permanent fix, if not then continue to look at other issues