Mark03

I have a 2003 3.4 L Chevrolet Impala. It will cut off while driving or rough high and low idling at a stop. The code called for random multiple misfires. I have replaced all spark plugs and wire, as well as coil packs. I've had the throttle body replaced, and still can't figure out why it continues to cut off. My fuel gauge continues to fluctuate between full and empty. Also, my ABS trac light will not go off. While driving, my car will sometimes slip when transitioning between gears. Please Help!! 😔