I don't want to hi-jack the thread but I have a similar problem on a 2003 American Tradition. My problem is the specifications say I have a 150 gallon tank,the gauge seems to work correctly but when it registers empty I can only put in about 100 gallons, never more than 104 and usually 90-100.It has been this way since we got it 4 years ago.It may seem like a small problem but knowing I could go another 200- 300 miles could be the diference in making it to a state with less expensive fuel.