well, pulled all the plugs out to take a look and it's not good. All are equally sooty so the engine has obviously been running rich and without a good blast that problem isn't going to sort itself out. Al that muck isn't going to help with getting a good spark.
I'll try cleaning them up tomorrow night and give it another run as the various short runs over the last year or so may have been enough to clog them up. Now that the O2 sensor isn't exposed to atmosphere, that should help too.