SEFI will have individual drivers for each injector. Of the two wires going to each injector, the VREF (+12v) wires will all be the same color. The driver wires (ground) in bank-fired systems will be 3 and 3 (3 injector wires one color, 3 injector wires another color). With SEFI, each injector will have a unique color code for the driver wires.
So, as confusing as I made that, you should be able to peek at the plugs/wires at the injectors or bulkhead connector to figure out what you have.