Seriously another alternator question.

Just tossing this out there...

What size is your crank pulley?

Getting full charging voltage (yes it is a bit too high) at idle is unusual.

If crank pulley is larger than stock or the alt pulley is smaller than stock could cause the alternator to spin faster and charge better at idle. still not the cure for the voltage being high
All stock. Pulley wise. Diameter of alternator pulley is possibly a tad larger as he installed a new pulley since mine would not clean up on a lathe. The ā€œVā€ was too damaged and he was afraid I would chew belts. But a larger pulley would slow down the alt .