I'd take a look at the FITech website support tab for instructions on your EFI. If you have an in-tank pump or even external hi-pressure EFI pump it needs a return line so the pump is not being deadheaded (not good at all for the pump banging its head against a brick wall)
Example of the FITech I used to run:
https://secureservercdn.net/198.71.2...ns-8.14.20.pdf