This is general advice for sideboarding with the deck. It may need to be adapted based on what you see of their deck, but the general reasoning behind choices should be solid.
Against Affinity
OUT: 3 IoK, 3 TS
IN: Anger, Damnation, Finks, Stony, Kalitas, (option)
Final card in can be a second Finks or Kalitas, depending on your read of the matchup. They dump their hand so fast and need little mana to operate, so the hand disruption and mana denial plan isn't that strong. Stony is great but don't go mulliganing to find it; you have more than enough main deck tools to stop anything but an Etched Champion with metalcraft.
Against Jund
Jund is hurt more than we are by RIP and game 1 they'll see virtually no creatures from us except Souls tokens. Punish their lands and bring in the value creature plan to wrong foot them.
Against Abzan Company
OUT: 3 IoK, 3 LotV, Gideon Jura
IN: Anger, 2 Kalitas, RIP, 3 Surgical
Our removal can keep them off the beatdown plan so we need to focus on not dying to their combo before Nahiri can do her thing. Aggressively mulligan for Surgical and removal. Since Emmy refreshes our library (assuming no RIP...) we can deck them even with infinite life from the Finks combo, but Redcap is dangerous.
Against Big Kid Abzan
OUT: 3 IoK, 3 TS, 3 LotV
IN: 3 Fulminator, 2 Kalitas, RIP, Damnation, EE, 1 Finks
Discard isn't important here and they have too much value. Focus on keeping the board clear. EE is for Souls tokens.
Against Dredge
OUT: 3 IoK, 3 TS, 3 LotV
IN: 3 Surgical, RIP, Anger, 2 Finks, 2 Kalitas
Surgical should be prioritized on Bloodghast, Narcomoeba, and Prized Amalgam in roughly that order. These three are their army and core to the engine. Don't snipe their dredge cards; if the deck survives the GGT ban it will be on the strength of these. Snapcaster flashing back a turn 0/1 surgical is virtually game right there so mulligan aggressively.
Against Bant Eldrazi
OUT: 1 Bolt, 3 IoK
IN: Damnation, 3 Fulminator
Reality Smasher is our biggest problem here, no pun intended. The inclusion of Fulminator makes it even easier to activate Revolt so you can Push their TKS.
Against Delver
OUT: 3 TS, Gideon
IN: Anger, 2 Finks, (varies)
If they're Grixis with Tasigur/Angler or RUG with Tarmogoyf/Hooting, board in RIP as the fourth card. If they're on Pyromancer instead bring in EE.
Against Grixis Control
-OUT: 3 Bolt
-IN: 2 Kalitas, RIP
Our mainboard is already pretty good against them. They will likely bring in additional counters to disrupt us and there's not much we can do about it. You might consider shaving the final bolt and a Push for Finks if they seem heavy on negate/countersquall but weak to resolved creatures. Don't bring in Surgical.
Against Burn
OUT: 3 TS, Gideon
IN: 2 Finks, 2 Kalitas
Optionally, for Naya Burn you might be tempted to bring in Fulminator to keep them off splash colors. There are several ways you might accommodate this which depend on their creature density. Shaving Terminates and/or LotV are options here.
Against Death's Shadow / Infect / Bloo
OUT: Gideon, (others)
IN: Varies
These matchups are very favorable. Bring in all 3 Fulminator and Anger versus Death's Shadow as their mana base is extremely fragile, cutting 3 Thoughtseize.
For Infect and Bloo just bring in EE.
Against Tron
OUT: 3 Push, 3 LotV, Gideon
IN: 3 Fulminator, 3 Surgical, Stony
This is by far our worst matchup. Game 1 is almost stone cold unwinnable and games 2/3 are tough. Attack their hand early, put up a board presence, and pretend you're an aggro deck. You won't win the long game even if you can exile one of the Tron lands with Surgical+Fulminator/Ghost Quarter. Be willing to drop a Snap into play T2 just to get a clock going if you don't have a better play.
Against Lantern Control
OUT: 3 Path, 3 Push, 2 Terminate, Gideon
IN: EE, Stony, 3 Surgical, 3 Fulminator, 1 Finks
Dead cards brought out for some real value as well as desperation creature threats that Bridge will likely shut down. Emmy keeps us from being decked so long as she's not exiled, which may happen with Pyxis. Getting EE on 1 to take out a Pyxis and then Surgical it away should probably be your primary goal. If either LotV or Nahiri can land without a Pithing Needle on them we may be able to break out but this matchup is tough. Like Tron and Valakut, if Lantern is common in your expected meta you will need to tweak the sideboard for Wear//Tear, Rakdos Charm, or another copy of Stony Silence.
Against RG Valakut
OUT: 3 Push, Gideon, 3 IoK, 1 Bolt
IN: 3 Fulminator, 3 Surgical, 2 Finks
This is another tough matchup. They go big, and quickly, and we have no ways of interacting with their game plan. Pressure them early, attack their lands, and hope you can snipe Through the Breach or Scapeshift with TS.
Against Ad Nauseam
OUT: 3 Path, 3 Push, 2 Terminate, Gideon
IN: 2 Fulminator, 2 Finks, 3 Surgical, Stony, EE
Disrupt their hand and try to apply early pressure. If you can force them to fog you, Surgical if so they have fewer outs for safely casting a big Ad Nauseam. Fulminator is for (mediocre) beats more than for keeping them off land since they can go off without many lands in play. EE takes out Phyrexian Unlife. If they go off they have more counters than we can throw at LabMan so there's no point to sandbagging Bolts. There's nothing we can do about Lightning Storm, of course.
