Rarely is anything terribly wrong with the EFI unless you had a fire, got rodent damage, or got flooded.  Corrosion/connectors/bad grounds are usually the major culprits. Each part can be tested for function right from the ECU connector, with the aid of a factory manual, some good probe pins, and a multi-meter.  The injectors and fuel pressure are pretty easy to validate as well. Even a spare brain can be bought used for very little cash. Â