I like being able to view fuel trim with this tool.
Fuel trim is the mystery variable behind the EGR fuel savings theory. It's where the 02 sensor data goes: constantly into Short Term to maintain stoich. Short Term, when it maxes out in either direction, informs Long Term and then resets to 0 to start all over again.
More details about fuel trim:
http://72.14.203.104/search?q=cache:...n&ct=clnk&cd=4