Quote Originally Posted by RedHeartbeat View Post
In the tune is a section for high octane and another for low octane. When you have low fuel and shut the truck off and refill the tank the PCM defaults back to the high octane tune section. If it encounters knock or ping then it drops down to the low octane tune. I'm not exactly sure of how the logic works to get it back into the high octane section of the tune again. I'm not sure if that is what your issue may be.
I was unaware that the computer would do that if it sensed knock/ping. I had someone do the tuning for me so I will contact him and see what he says.