Mutagenic Growth: Against R or B decks with sweepers
Journey to Nowhere: Definitely against any white deck (Standard Bearer)
Moment's Peace: Aggro match ups
Standard Bearer: Against any faster aggro-combo deck and the mirror
Temporal Isolation: Spot removal
Gleeful Sabotage: White decks and anything with artifacts/enchants
Hornet Sting: Spot Removal

Generally you are taking out the slower enchantments like Favor of the Overbeing and Armadillo Cloak, sometimes Rancor if you don't need the trample.

Affinity
Journey to Nowhere is good if they showed you Atog. I would take out 1x Favor of the Overbeing and 2x Aura Gnarlid for some spot removal in this case.

Black aggro
-3 Favor of the Overbeing, -1 Ancestral Mask | +4 Moment's Peace

Burn
-3 Favor of the Overbeing | +3 Standard Bearer

Counterburn
-2 Favor of the Overbeing | +2 Mutagenic Growth

Delver Fae
I recommend taking out a few 1cc enchantments, as they are prime targets for any removal spell they have, especially Spellstutter Sprite. -3 Rancor, +2 Journey to Nowhere, +1 Hornet Sting

Dimir Teachings
-2 Favor of the Overbeing | +2 Mutagenic Growth

Eye Candy
-3 Favor of the Overbeing, -4 Armadillo Cloak | +4 Moment's Peace, +3 Standard Bearer
Spot removal might also be useful over Aura Gnarlid

Goblins
No boarding to do, unless you feel the need for removal.

Infect
-3 Favor of the Overbeing, -4 Armadillo Cloak | +4 Moment's Peace, +3 Standard Bearer
Spot removal might also be useful over Aura Gnarlid

Kuldotha Boros
-2 Favor of the Overbeing | +2 Mutagenic Growth

MBC
-2 Favor of the Overbeing | +2 Journey to Nowhere

Stompy
-2 Favor of the Overbeing | +2 Moment's Peace.

Tron
Spot removal such as Journey to Nowhere might be useful. Other than that, there isn't really any sideboarding to do.

White Weenie
Board out some of the more expensive auras and get Journey to Nowhere. Any spot removal that you have will be useful here.

Winter Zoo
No sideboarding unless you see Circle of Protection: Green. Then you need the Gleeful Sabotages