The charging voltage wil change depending on the outside or ambient air temperature. The warmer the weather, the less voltage needed to keep the battery fully charged, cooler weather requires a higher charging rate.
In the past with external voltage regulators the voltage was adjusted to within a certain voltage "window" depending on the average anticipated temperatures. Set too high for the warm temps, and the high voltage would boil off a battery, too low in cold weather meant low a low charge, and possibly poor cranking performance on those cold winter mornings.
The internal regulator alternater systems really helped to eliminate twice / year voltage regulator adjustments, and provided for a much more durable, and reliable charging system, and increased battery life.
Most likely you probably see 13.5 - 13.9 volts on warm days, and 14.2 - 14.6 on cold days, in between the voltage may fluctuate from 13.8 - 14.1 depending on the number of accesories drawing a load. The battery may be used in reserve if the load is greater than the alternator can supply, and the additional charging may be noticed.
On performance chips, most chips are programmed to provide the additional performance at Wide Open Throttle (WOT). There are some that can be found that may provide enhanced performance at other than WOT, up through the normal RPM range, but they are few and far between.
If you are planning any modifications to the intake, exhaust, or heads/cam package, you would do well to wait until the modifications are completed. Then have a custom program flashed to a chip based upon the modifications made, and what you want out of the enhancements. Hope that filled in the blanks for you.
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