Hey AK--I do not doubt your service tech knowledge, but I have never put anything less than Top Tier Gasoline in my tank--and my float is waaaaaay jacked up. I highly doubt it is the type of gas people use. It is all in the design of the float and sending unit. How come other manufacturers don't have the same issue with their fuel pump sending units? My 1990 Honda Accord has never had problems reading the exact amount of fuel in its tank--and I do not care about the quality of gasoline that goes in that thing...but it reads true, even after 18 years. Even the OBS trucks had the same issue--partly due to the fact that they have the same design (relatively) that the NBS truck's sending units do. I run fuel injector cleaner through it every now and then and it hasn't cured my faulty sending unit problem--ever.
Like I said, I am not calling BS on you, its just that I know it is in the design of the unit and electrical connectors--not the grade of gasoline...