In case anyne cares...

The new Mass airFlow Sensor had no effect. But I noticed that there
was some slight leakage around the vacuum hose going to the PCV valve.
I put a new hose clamp on it and my problem has all but gone away. So
I am guessing that there is a very slight vacuum leak somewhere that
was causing the problem. The leaks all added together made the idle
rough, and when the engine sputtered, the sensors all went out of
range.

-Dan