Tim, the issue may be a bad MAF that's throwing an O2 sensor. Or it's one of your oxygen sensors. The computer gets quite confused sometimes.
If you have not changed your oxygen sensors, you may want to do them all if you find out it's an oxygen sensor and not the MAF. You can buy Bosch replacements from
www.oxygensensors.com for $110 each or so and install them yourself in a half hour. Really!
You'll love the better fuel economy, steady idle, and better performance that a complete new set of sensors provide. Do not replace just one... the higher sensitivity of the new one will throw codes on the others sooner than later.