Sorcerer Improved Empowering I + Skiver

[swaix1982]

The skiver gives Efficient Metamagic - Empower II, the description is "additional SP cost for Empower metamagic is reduced by 2 SP", as I know it doesn't stack with Sorcerer Improved Empowering II, but does it stack with Sorcerer Improved Empowering I; will I have 4 sp discount if I get the enhancement and I wear the item or will I have 4sp discount only wearing the item?

[Arctigis]

The skiver gives Efficient Metamagic - Empower II, the description is "additional SP cost for Empower metamagic is reduced by 2 SP", as I know it doesn't stack with Sorcerer Improved Empowering II, but does it stack with Sorcerer Improved Empowering I; will I have 4 sp discount if I get the enhancement and I wear the item or will I have 4sp discount only wearing the item?

Items stack with enhancements. Sorcerer Improved Empowering II would net you a -4sp reduction on empowered
spells. Skiver would net an additional -2 SP saving for a total of -6 per cast.

Efficient Metamagic on items does not stack with other items (e.g. Efficient Maximise I on the Greater Cunning
trinket does not stack with Efficient Maximise II on the Arcane Shard or Epic Ornamented Dagger)