[tephra]

no problems!

so Chris - can you confirm that:

with the gauge OFF =
OMH meter between white and black shows around 1 ohm (ie some continuity)
OMH meter between white and brown shows 0.L (ie no continuity)

with the gauge ON =
OMH meter between white and black shows 0.L (ie no continuity)
OMH meter between white and brown shows around 1 ohm (ie some continuity)

if thats the case then:
1) reconnect the white output back to the ECU pin (ie where you had tapped into before - you had cut the existing wire obviously because your ECU was reporting that the fuel temp sensor had an error)
2) connect black wire to a 250ohm (ish) resistor, then then the resistor to ground.

quick explanation:
When the ECU sees the voltage go ABOVE the threshold (ie no continuity condition) it will start the timer to swap to alternate maps.
When the ECU sees the voltage go BELOW the threshold (ie some continuity) it will INSTANTLY swap to normal maps.

Lastly is DHB linked or not?