The Pro-M EFI Engine Management System for 1979 – 1985 Fox Body Mustangs includes our fully programmable Pro-M EFI PCM, tuning software and a custom Mustang powertrain wiring harness. Your New Pro-M EFI wiring harness will be made to fit your specific model year Mustang. It is not a universal harness. It installs in the car just as if it had been made by the factory, and uses all the same sensors, connectors and circuits as the OEM harness.