More air equals better performance. The Duramax L5P 6.6L intake features three air inlet points. If you want to customize the amount of air you take in, we provide an optional box plug that can seal off one inlet point.

When to use the Box Plug?

Stock intake boxes are a significant contributor to poor airflow which is why S&B designs custom air boxes with secondary and/or enlarged openings. With that said, S&B recognizes the benefits of cooler air, so we have included a plug to seal off the opening if desired. For optimal performance, we recommend that the intake be used without the box plug, except in conditions of an extreme heatwave.