Delver
Out
-3 Corpse Cur -Seal or Strength
In
+4 Scattershot Archer
Anti Delver Package
Affinity/Hexproof
Out
-3 Seal of Strength, -2 Rancor -1 Corpse Cur
In
+4 Nature's Claim +2 Naturalize
The Anti Enchantment/Artifact Package.
MBC
Out
-3 Seal of Strength
In
+1 Corpse Cur +2 Apostle's Blessing
You should be able to race them in a Match where life totals don't matter at all. The Corpse Cur gives you more recursion, and the Blessings more protection from removal.
Tron
No Sideboard, keep a super aggro hand, and beat them before turn 4. Infect is designed to beat decks like this.
Delver Fiend
No sideboard, both of you are playing decks that try and shorten the life total, its a total race, don't keep a hand that doesn't do anything.
Slivers/Goblins/ Stompy/White Weenie
Out
-1 Viridian Longbow, -1 Seal of Strength
In
+2 Apostle's Blessings
Protection can help you get past blocks, pump can end the game much more quickly.
Boros Kitty/ Azorious Kitty
Out
-1 Viridian Longbow -1 Corpse Cur
In
+2 Apostle's Blessing
These decks want to grind, midrange, and gain life. You don't care about life, just poison counters. The Blessings help you get in there.
Burn
Out
-2 Seal of Strength -1 Virdian Longbow
In
+2 Sylvok Lifestaff +1 Corpse Cur
Life gain, should keep you a little ahead of the race, they do have to kill your stuff to stay alive. So you should have the edge. The extra Cur for extra graveyard love.
MUC
No Sideboard, Elf into Rancor turn two they will be able to do very little to stop you. Again Infect is designed to take out decks like MUC.
Tortured E.
They want to durdle, you want to win super quick, no board needed. Again you need to keep a hand with a 1 drop and some pump to get in there.