When Should I Install or Remove the Optional Box Plug?

Many S&B cold air intake kits include an optional box plug. This plug allows you to choose between maximum airflow or maximum protection depending on your driving environment and performance needs. This guide explains when to keep the plug installed — and when removing it can improve airflow.

S&B Air Intake Box Plug Diagram

When Should You Remove the Box Plug?

Removing the box plug increases airflow by allowing the filter to pull air from an additional opening in the airbox. This is useful when:

  • You want the most airflow possible.
  • Your vehicle has performance upgrades (tunes, exhaust, turbos, etc.).
  • You drive mostly on paved roads or in light-dust conditions.

Note: Removing the plug exposes the filter to more dirt, requiring more frequent cleaning.

When Should You Keep the Plug Installed?

Keeping the plug installed seals the extra opening and ensures the filter is only pulling air from the factory cold-air source. Leave the plug in place if:

  • You drive in hot climates (reduces intake of engine-bay heat).
  • You drive in dusty, sandy, or off-road environments.
  • You want longer intervals between filter cleanings.
  • You prefer maximum protection over maximum airflow.

Frequently Asked Questions

Will removing the plug increase horsepower?

It may help high-demand engines breathe easier, especially with performance upgrades, but results vary by vehicle.

Does removing the plug allow hot air into the intake?

Yes — but the effect is minimal during normal driving. In hotter climates, it’s better to keep the plug installed.

Will my filter get dirty faster?

Yes. With the plug removed, the filter is exposed to more open airflow and may require more frequent cleaning.