Under high-boost conditions, the stock actuator's weak spring allows the wastegate to blow open, limiting midrange torque. Bleed orifices (also known as "boost foolers") just make it worse. Only Banks solves this problem by replacing the boost actuator. BigHead holds the wastegate closed for quicker boost, then controls the opening to maintain peak boost for superior acceleration and mid-range pulling power. Power Now! When turbo exhaust backpressure increases, the stock actuator prematurely blows off the seat, softening boost in the midrange and killing torque. With twice the diaphragm area and spring pressure of the stock wastegate, Banks BigHead Wastegate Actuator keeps the valve seated longer and achieves a higher peak boost, sooner. At peak, BigHead opens the wastegate and holds its position, for precise boost control that gives you crisp acceleration and more mid-range pulling power. For trucks manufactured in 1998. Build date can be found on vehicle information tag driver door jamb. Replacement part for PN 47521 EO D-161-110 and D-161-58 Key Features: Quick, Controlled Boost. Produces massive torque right from idle. Doubles stock's diaphragm area and spring pressure. Keeps the valve seated longer achieving higher peak boost, sooner. Crisp acceleration and more mid-range pulling power. Fits Ford 7.3L (1999-1999.5) manufactured in 1998