the issue with cooling ducts is not performance; they're totally useful for track cars - its availability for different bumpers
for the 09-13 stock bumper, Stillen has you covered with an easy bolt on kit
The same kit also has optional parts to work for their own Stillen bumper (but it fits like ****)
for the 09-14 Nismo bumper, Nismo makes ones that require cutting but otherwise has the right contours to bolt up after u make the right opening. This design has been copied by Finite Element and Synergy composites as cheaper options
All other aftermarket bumpers and the 2015+ Nismo require custom work, like buying a universal duct and likely adapting the Stillen hose and backing plate kit
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