I just did the zxt alternator swap this weekend to my 260z. I am getting a 13.2v at the battery, down to about 12.1v during cranking and back to 13.v while running, if I rev the car from the engine bay watching the meter, I volts creeps to 15v and stays there. I will have to double check my wiring or maybe the alternator is bad -over charging the system?