Big Evil - I'm going to look into the diff speed sensor. The transmission specialist guy I have talked with in the past probably has the right test equipment to see if that sensor is outputting bad data, as well as the TPS.
3050rpm, that writeup was informative, but what I appreciated even more than that was that they were committed to 'learning' something, even if it meant paying for work that turned out to not fix the problem.
I'll call him on Tuesday and see what happens. I'll report back here.