4c Artifacts plays almost no early creatures worth killing with Burst Lightning or Impractical Joke, instead grinding value through artifacts like Simulacrum Synthesizer, Candy Trail, and The Mind Stone, so those removal spells are largely dead weight. Spell Pierce taxes their artifact spells and disrupts their sequencing, since this is a deck that wants to resolve cheap permanents uncontested. Extra Ghost Vacuum copies are mainly graveyard hate: they can exile artifact cards from their graveyard, which denies fuel for crafts like Clay-Fired Bricks and Spring-Loaded Sawblades. Note that Pinnacle Starcage exiles artifacts with mana value 2 or less, so our Vacuums are vulnerable to it. Keep pressuring with our elemental threats, but don't overcommit, since they have real answers in Perilous Snare, White Auracite, Erode, and Day of Judgment.