LS engines have both MAF and MAP sensors, and use them both. In general MAF is best for transient conditions and MAP is best for steady state. So MAP is most important for idling. On the other hand many idle problems are not idling per se, but a bad transition from idling and back to idling. If the MAF fails on a stock LS, it will run on speed density (MAP).My ECU is different than yours since mine has a MAP sensor and an LS uses a MAF sensor for measuring airflow so I'm not sure if that affects anything but the IAC principles should be the same.
You're right about the IAC count being the way to monitor minimum air. The TPS signal must also be within a recommended range near zero.