Don't feel bad--I have three of them sitting on the shelf, all good.
Replaced them in exactly the same way you did. See Dennis' post, as usual.
The only thing I would add is that there may be something else you bumped
around in there while doing the T2 that made it temporarily run better, like
the little green coax wire to the O2 sensor.

I've found that cleaning the connection with an acidic cleaner works pretty
well, then coating it with clear high-heat spray varnish to prevent it from
corroding again. Or at least soon.