Ben--the lean condition is happening cause the PCM is not getting the reading after the cat it wants. There is obviously too much unspent exhuast gasses passing through the cat--so the PCM is cutting back fuel. I would do the easy/cheap stuff first--have the O2 sensor checked to see if it is good still (they go back QUICK if the cat has gone south), check fuel pressure on the Schrader valve by the TB (looks like a valve stem on a tire), and tap on the cat with a bunt hammer to see if it rattles. After that, do a new cat. It should fix the problem...