They shouldn't be needed with the Stillen or Takeda. The Nismo CAI comes with them. The AEM and Injen do not include them, but they may need them. Those intakes are of similar design to the Nismo. Who copied who, it's tough to say...
I'm sure there are other intakes out there that I am not mentioning.
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Competition Clutch|Fast Intentions|Maxbore|NST|Setrab|Stillen|Tomei|Uprev| Z1
Avant Garde|SPC|Stance|Whiteline
Aerojacket|Seibon|Tanabe|TRS|TWM
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