VERY similar to what my Graphite did at around 100,000 miles.

Twelve plugs and 12 wires did the job for me. I had a handful of O2 and misfire codes, the O2 codes were all indicating O2 was 'too high' and/or 'out of range high'.

Sorry, it's been four years, I can't remember the exact 02 codes but I had no less than six misfire codes. Car was fine, sitting there idling. Started up like a new car, just don't 'get on it'....

The codes will probably tell you enough that this thread was not even necessary. Of course, being a '6, you have more to deal with than a simple N/A does.