here lately it has been shutting off for no reason at all.

After replacing the Thick Film Ignition module, checking the fuel pump and pump pressure is in order to make sure the pump is not stalling or being starved. Also, reset the fuel system inertia switch at the rear of the car just to be sure it is closed. The EEC IV key-on-engine-off and engine running codes should be read for possible clues to the stalling condition. Not as likely, however the ignition switch or its plug in electrical connector could be a fault since it is a know problem area of Ford products. In addition to the ignition switch, the 10-pin (salt and pepper shaker) connectors of the engine wiring harness may be at fault as they had been a problem area in earlier model year Mustangs. Faulty or poor EEC IV grounds or engine grounds could also cause a stalling condition due to vibration.