Erratic volt meter after changing alternator

On my 97 K1500 5.7 I changed my alternator after the old one died. When I replaced it with a new 110Amp my v olt meter in the car bounces from 12 to over 16V while driving and sometimes while idling after it becomes erratic.

The lights (headlights, overheads, dash, tail lights, blinkers) all flash from dim to bright. I have 2 600W amplifiers for my speakers and subs. The amps do not lose power and the head unit does not dim with the other lights. When the amps are unplugged I still get an erratic reading.

Alternator battery and everything autozone could test came back "100% positive"