49k is kind of low mileage for O2 sensors to go, but you never know. They're pricey enough to verify at least one is bad before replacing the set.
I'll keep that in mind. What do you think about the Daniel R comment that, if it's an O2 sensor, more than one cylinder would be involved? (Not trying to start any fights here 
---just wondering.)
Have you considered investing a Durametric?
Yeah, I have, and I'm definitely interested at some point. (Over the last couple of months we've had an number of unusual expenses---repairs and stuff---and I really hate to invest in the Durametric right now. But, getting one is probably on the horizon not too far off. Maybe when the family asks what I want for Christmas...)
In the meantime (as soon as I get the chance) I need to have someone give me a readout so I have current info. (I don't even know for sure it's still the same code as it was when I got the CEL a few hundred miles ago.) Question: Do Porsche dealerships typically charge just to plug it in and give someone a readout code??
Plugs are relatively cheap @ ~$9-$10 apiece (I got OEM Berus from Sunset). If you don't know when they were last changed or it's been a while, change 'em. Some plugs are a little tougher to get at than others, but they're all really pretty easy with the wheels off. And for about $60 more you can change all your plug tubes and the inner and outer seals while you're in there doing the plugs. Mine weren't bad, but they're so inexpensive and easy to do, I figured why wait 'til they bite me. There's a good DIY article on this on Pedro's site.
Also a project I've had on the radar screen. This is the time of year I typically do this kind of project (ie when I tend not to drive the Box all that often), but I need to free up some garage space and work it into the schedule.
On the coil packs have you considered swapping #1 with another one to see if #1 still gives you a misfire code?
Good idea. Again, it would be nice to have the Durametric on hand when I did that...