Keeping the original instrument-analog gauge and connecting ST107 in parallel to the guage?

ST107 can be connected in parallel with the analogue fuel gauge with the resistive tank sensor but not on resistive inputs on ST107 (R1 to R4).

Connect the common GND from the gauge (or check that the common GND is connected to the negative terminal of the battery) to ST107 GND. Connect the signal input on the gauge to the voltage input on ST107 (U1 to U3) and not to the resistive inputs R1 to R4.

At least two voltage calibration points have to be input on Pico.