First there was a substantial amount of metal shavings found in the rear diff. Okay, replace the ring and pinion. Next, the front CV joints start clicking/grinding/binding. Fine, replace the CV joints. Now, the turbo seems to have "gone out" and the thing runs WAY too rich. On the way to the Subie dealer, I was practically leaving a smoke screen behind me under heavy throttle. I don't beat the car. After the metal shaving incident, I've actually kind of babied it. Am I the only one having this problem?

Yes.

I'm driving a lightly modded '06 and have never had an issue with it - nor with any of the other Imprezas I've owned.

Sounds like the car was abused in its childhood.

I did buy it used which, for an STi, could be risky. People tend to beat those things harder than a dime store hooker then sell them.