Fuel Sending Unit
 

I just purchased a 2007 RX-8 and the fuel indicates only half full when I top off the tank. I suspect the fuel sender unit but am unsure if there are any after market modifications to limit the fuel for weight/performance issues. Has anybody experienced the same condition?

There are 2 sending units...one in either side of the tank...easiest way to tell is to unplug one side and see if it changes on the guage...if it does...it is the other side

Often it is just a broken wire...especially if your fuel pump has been removed and replaced ever