Zero ohms = Empty
~ 30 ohms = Full
~13 to 16 ohms = 1/2

The tank level sensor has a metal stop for empty and full.

Remove the gauge wire on the tank. Ground that wire. The gauge must read empty.
If not, do you have a 6 or 12 volt battery and if 12 volt, what voltage dropping device are you using?

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."