Power Loss

[92NJSVX]

Ok, im stumped. When the car is warmed up and running at idle the car loses power when I turn the lights and heater on. When I tap on the gas the volts go up.
The Alt is a new 95amp and battery is only 8 months old. At idle the car will read 12.43-12.50 volts when the lights and heater is turned on. When they are off it reads in the high 13 to low 14 volts.

Anyone else have this issue? Any help is greatly appreciated.
Cheers,
Adam