I like your build here. If you're looking at burn, Boros Charm is an auto-include. It's just too versatile and powerful to pass up. And Spark Elemental is just another bolt that you can only aim at your opponent's dome, you should consider replacing it with Grim Lavamancer for value. Also, depending on how much you like your critters, consider the Academy-acclaimed Legion's Initiative, which won this year's "Coolest Screw-you to Field Clears" award.

Solid list! I do have a couple suggestions though. I really don't think that you should have so much creature-specific burn (Searing Blaze and Searing Blood). Some are needed, but there are many other burn cards that can be included instead. Consider splashing white and/or black for certain cards. Bump in the Night is a Lava Spike but better, and Lightning Helix and Boros Charm are solid cards for white burn. Spark Elemental isn't doing any wonders for this deck either. Seriously, it is like 25 times worse than Lightning Bolt or even Shock and Lightning Strike. Use Grim Lavamancer or Goblin Guide instead, the deck WILL perform better.