Awesome work man.
All flex fuel sensors I used so far, were frequency base, not an analog 0-5v output. What sensor does your patch uses?
Its uses the standard GM style flex sensors, I'm just using a pwm to analog converter. The plan was to use the pwm signal from the egt sensor input but honestly pwm to analog seemed easier, did it a few years ago on a subaru project I was working on and it worked fine. You can make them with an Arduino, finished sketches are even out there if you look for them. That or buy a legit one.