Does anyone have any advice on inherent problems with the 3.0 quattro that I need to watch out for.

I bought it with 66k miles. I just changed the oil, tranny fluid and center diff fluid.

The 1st Owner just replaced both cat converters.

Any insight would be appreciated.

 

A little late for this question, isn't it?

 

Did you change the tranny filter also?
Check oil leaks, both air filters, cabin and engine.