Voltage, can tuning affect this?
it hasn't. I believe it's an alternator / regulator problem.
The field current has to run higher to make demanded
current, when shaft RPM is less. This puts max power
dissipation onto the field current driver in the alt regulator
and I believe it goes into some sort of thermal limiting
(because I only encountered this on hot days, max
electrical load).
You might want to check the load-bump idle airflow stuff,
as well as raising the base idle RPM to some more stable
(i.e. more room to bounce, before dying) value.
My idle with ac on right now is 950rpm (Big cam)

