Though the threads were easy to read, the solution is vague at best:
1) check resistance from TPS
2) clean TB and MAP sensor (MAP sensor already done by me)
3) replace w good TPS if you have one
I got a new one online for $30 and could just throw it on...
Looking down barrel of the TB w the snorkel removed, it looks pretty good (I've seen much worse looking TB pics online)
No other codes appear (after I cleaned the MAP sensor a while back) other than this silly P0120 and derivability is not affected as far as I can tell.
Since the code appears and then clears itself within a few startup cycles I'm almost inclined to ignore it, but I'd like to know if it is a sign of a future failure brewing.