Dinan High Flow Intake System - 2003-2005 BMW Z4"This seemingly simple yet very effective approach to the business of improved intake efficiency consists of a replacement lid for the stock airbox designed to increase overall volume and accommodate a high flow filter element. The lid is molded from a special composite material, chosen for its ability to resist power robbing under hood heat. The lid also provides for a completely sealed air box, maximizing pressurization for optimum performance.