Everytime I had lean bank 1 and 2 it was a dirty MAF. Tour 2 had rough idle a few times but no codes (it is OBD I) and it was an ignition problem every time. Bad coil pack once and 2 bad plug wires over the years. You will hear a misfire in the exhaust stream. Misfire usually will show up as rich, not lean. Like BW said, look for vacuum leaks too. Could be loose hose clamps, cracked vacuum lines, intake manifold or injector gaskets. Use the carb cleaner method of looking for leaks if you are careful. Spray it around the gaskets and see if the idle changes.
