1998 Mustang GT Strange happenings when accelerating

I have a 1998 Mustang GT with a 4.6 engine. When acceleraring to 3500 /4000 rpm the ABS, battery and another light on the dash comes on, the a/c fan speeds up to about 3 times faster than normal and the cd player stops. The engine continues to accelerate, even up to 5000/6000 rpm. When the engine decellerates below 3,000 rpm the lights on the dash go out, the fan returns to normal and the cd player resumes play. What causes this??