Keep in mind that an EFI system does not use much current.
That's really not the issue. A clean constant voltage is a concern.
The injectors out put can vary with a change in voltage along with the fuel pump output. So at low voltage you get less fuel. This can play havoc with trying to tune the EFI. But, the GM system is capable of learning and will adjust and compensate for some of the variables.
The biggest draw is the electric pump and the ignition. So if anyone with a carb has installed an electric fuel pump then it's really not much different.
