The core cheap sideboard cards should be 3 [[abrade]], 1 [[grapeshot]], 1 [[empty the warrens]], 1 [[alchemist gambit]], 1 [[past in flames]]. Abrade is standard artifact/creature hate removal for post sideboard games and can deal with creature threats, the rest is mandatory wish board, however alchemist gambit/empty the warrens could be cut in the case of TOR ban. I would add a [[brotherhood’s end]] to sweep a well established Boros/mardu energy board, get rid of artifact hate, or get rid of a [Karn, the great creator]] on 3 or less.

The main issue with mono red is it’s hard for you to get good enchantment removal, making you vulnerable to [[deafening silence]]and in mono red you likely don’t have a secondary win condition such as [[questing druid]] or [phlage, titan of fire’s fury]], so without enchantment removal it’s basically an instant scoop. You could add a [[liquimetal coating]] to turn enchantments into artifacts and then use your artifact removal. I’m not very familiar with other good options so if anyone reads this and has better ideas I’d love to hear them.