Boros Energy fills the board with small, low-toughness creatures like Ragavan, Ocelot Pride, and Guide of Souls, so Fire Magic cast as Fira for {2} to deal 2 damage to each creature sweeps most of their early board while leaving your bigger threats like Hollow One and Vengevine alive. The extra Lightning Bolt adds more cheap interaction for Ragavan or an early Ajani, Nacatl Pariah. Cut Burning Inquiry since giving their aggressive deck extra cards is too risky, and trim Practiced Offense since you want to be proactive rather than pump a wide board into their sweepers like Wrath of the Skies.