It is said in the manual:
Type of Feat: General
Prerequisite: Spell Focus Evocation
Benefit: When you cast an evocation spell that deals energy damage (acid, cold, fire, electricity, or sonic), you can choose for 10 points of energy damage dealt by the spell to become untyped damage to which energy resistance and immunity do not apply.
So how to choose whether to turn the 10 points or not? Can't find the switch in the radial menu...
PS: could the bonus feats of Element Savant (Elemental Focus, Elemental Piercing) work together with Archmage's Master of Elements? For example, if an Air Savant/Archmage turns Fireball into lightning damage, does the DC increase like casting Lightning Bolt?
Thanks!