What can cause my fuel gauge to go from a full tank when driving and look normal as it moves toward the empty then all of a sudden it shows full again with blind of an i and says I have more mile to empty then I know it can go.

What were the SCAN TEST results? ... Professional scan tool can easily determine if it's a signal problems or instrument failure.

One more important thing: please make sure you try and fill your fuel to 100% every time you fuel your vehicle. When you just put "some" fuel in, the computer gets confused a bit in this vehicle. That's normal. Also, it's essential that the power of the vehicle is entirely off when fueling, or it will confuse things as well. Meaning, dash lights totally off, radio totally off, and so on.