Put a 22K resistor in for R2 in the picture and it seems to read properly now. Apparently I was only reading the very low end of the signal before because with the calibration I was using it is reporting 10gph at idle now
I will adjust the calibration now and hopefully it should be all good. I will keep the laptop showing the injector pulse width and keep track of the MPGuino for a while and make sure it is long term stable but it seems about right now.