OK - here was the issue - it turned out to be a bad injector. I've had an injector that nailed when cold, and even nailed a little occasionally at mid-throttle. I cleaned it a couple times, and it would improve for a day or two then go back to its behavior. I got a single known good injector and swapped it in, and the nailing went away, and the idle improved IMMENSELY (and everything has gotten better - more power, better fuel economy - that one injector was truly the turd in the punchbowl). The only time the idle is noticeable is after a long drive, and I feel that the rack dampener bolt is the issue there (it is the old style).