Thanks. I saw that thread earlier, along with quite a few others on the idle problem. I haven't replaced the air mass sensor (since its a $450 part), but I don't believe it could be bad, because the car runs perfectly at everything but idle. Seems like there would be other problems... maybe I'm wrong?
I've already replaced the 02 sensor, OVP relay, wiring harness. I've checked for vaccum leaks and the coolant temp sensor.
Haven't replaced the throttle actuator ($900) but I don't suspect it because cruise control works fine - drove from LA to SF yesterday on cruise the whole way, without a hitch.
Right now, I'm suspecting the engine speed sensor, but I can't find much info about it in the tech manual or on the board.