An air driven diaphragm pump includes an performance control actuator having a housing with opposed air chambers. The pump includes pump chambers facing the air chambers and pump diaphragms extending between each air chamber and each pump chamber, respectively. The actuator further includes an air valve, an intake to the air valve and an engagement. The intake includes an intake passage and a performance control intake adjuster rotatably mounted. The intake adjuster has a helical channel and a closure element extending adjustably into the intake passage. The engagement engages the helical channel for control of the intake. The helical channel has varied pitch to provide a nonlinear relationship between rotation and axial advancement of the intake adjuster. The nonlinear relationship gives flow rate proportional to the angular rotation of the intake adjuster. The end points of the channel provide a practical minimum pump performance of about 40% of maximum pump flow rate and a maximum pump performance of about 97% of maximum pump flow rate.