A pneumatic distribution system for an agricultural implement, including a plurality of fluid lines including a primary fluid line and at least two secondary fluid lines, and at least one header fluidly coupling the primary fluid line with the at least two secondary fluid lines. The at least one header includes a header body having a fluid inlet fluidly coupled to the primary fluid line and at least two fluid outlets fluidly coupled to the at least two secondary fluid lines, a top cover connected to the header body, an insert located beneath the top cover and associated with the fluid passageway, and at least one actuator operably coupled with the insert and configured for moving the insert to control the airstream.
