I have an intermittent issue with the fuel gauge on my 05 Saab 9-3. When the tank is completely full, the gauge reads empty. When the level drops to around 7/8, everything goes back to normal. I have tried using a variety of cleaners, as I have read that there is a problem with sulfation of the sender wires. I have tried Techron, Berryman's, Gumout, etc. Nothing has worked. Is there anything else I can do?