Often a MAF problem is nothing more than a dirty connection at the MAF sensor. The connection can be cleaned by removing and reinstalling the connector about half a dozen times. It also helps to smear some dielectric grease on the connections when they are apart.
I also agree that it is not likely to be the MAF if it is effecting only one bank. Possible, but not very likely. I think that it is likely that you will need to replace an oxygen sensor, especially if you found that it "flat lined" when scanned.
The check engine light will stay on until reset on OBD II cars. Yours is acting normal.
Most definitely try what you can before trying an oxygen sensor.
If you have a K&N type air filter, you may have a contaminated MAF sensor wire if the filter was over oiled. Cooked oil on the hot sensor wire can throw off the accuracy of the readings. Cleaning the sensor wire is worth trying, but often must be replaced. When this happens, you usually get MAF codes as well as O2 sensor codes, and again you would most likely get codes for both O2 sensors.
I've rambled a lot, but I hope I may have helped.
