Gauges are irratic

[PumbaScout]

I am a new user of TunerPro and tuning in general. I am trying to set up an ECU for a 95 LT1 Caprice engine used in a 58 Chevy conversion. I have two 16188051 that I am programming and using for troubleshooting purposes. I made my own cable with an Arduino FTDI converter connected to D30 on the PCM. I Can connect and download data and also flash to both ECM with no problems. When I try to use the gauge function I am seeing all the outputs go crazy as soon as I start the car. I am not sure if I should be looking at issues with the cable (baud rate, comm settings), grounding issues with cable? Does the ECU need to be grounded? Or maybe the adx file that I started with is not right. I am just looking for a direction to start with. Any help is appreciated.