I found out about “Alternate ripple” that can cause some wild issues. I used a nice OBD2 tool and observed the voltage output, it fluctuates a lot between 14.3 to 14.9 volts.
Is this normal for an alternator?
If the charging system is of the ” normal type ” and not a “smart charging system” yes the reading are normal.
there are YT videos explaining a “smart charging system”
As to the surging issue:
Might take a look at this,
https://www.2carpros.com/articles/engine-surges
This will give some areas to check.