If you missus put normal unleaded in it and you ragged the living shit out of it, you might have blown it up. A compression test is the only real way to tell easily.

However, it might not even be related to the fuel fuck up and could be the turbo oil seals or valve stem seals (more likely the turbo). None of these things are easy to diagnose I'm afraid, especially if there wasn't a definate time that these problems started, or a big bang etc.