In an injection molding system comprised of an injection molding machine, a heated manifold into which the injection molding machine injects a selected injection fluid, a plurality of nozzles (1n, 2n, 3n, 4n) receiving injection fluid from the heated manifold, the nozzles each having a respective gate (1g, 2g, 3g, 4g) communicating with one or more cavities, each nozzle having a valve comprised of an actuator (1a, 2a, 3a, 4a) and a corresponding valve pin (1p, 2p, 3p, 4p) controllably driven by the actuator to control velocity or pressure of injection fluid flow through the gates of the nozzles during an injection cycle having a selected duration, the injection cycle comprising a fill phase wherein between about 90% and about 99% of the mold cavity is filled with injection fluid and a subsequent pack phase wherein between about 1% and about 10% of the mold cavity is filled with injection fluid, a method for establishing pack and fill pressures of the injection fluid injected during the pack and fill phases at preselected positions within the cavity of the mold, the method comprising: selecting a target fill and pack pressure at each of the preselected positions, injecting injection fluid on a first injection cycle through each of the gates (1g, 2g, 3g, 4g) of each of the nozzles (1n, 2n, 3n, 4n) with the corresponding valve pins (1p, 2p, 3p, 4p) each being positioned at corresponding first selected axial positions relative to each of the gates, recording the pack and fill pressures at each of the selected positions within the one or more mold cavities during the first injection cycle, establishing second axial positions for each of the valve pins (1p, 2p, 3p, 4p) relative to each of the respective gates (1g, 2g, 3g, 4g) that are determined according to an algorithm that determines an adjustment in the axial positioning of each of the valve pins relative to their respective gates that will effect an increase or decrease in the fill and pack pressures relative to the recorded fill and pack pressures that more closely approaches the selected target fill and pack pressures, injecting injection fluid on a successive injection cycle through each of the gates and controlling the actuators (1a, 2a, 3a, 4a) corresponding to each gate (1g, 2g, 3g, 4g) to adjust positioning of the valve pins (1p, 2p, 3p, 4p) to the second axial positions for each of the valve pin that are determined according to the algorithm such that pressure or velocity of flow of injection fluid through the gates is adjusted to more closely approach the target fill and pack pressures for each of the selected positions within the one or more mold cavities. selecting a target fill and pack pressure at each of the preselected positions, injecting injection fluid on a first injection cycle through each of the gates (1g, 2g, 3g, 4g) of each of the nozzles (1n, 2n, 3n, 4n) with the corresponding valve pins (1p, 2p, 3p, 4p) each being positioned at corresponding first selected axial positions relative to each of the gates, recording the pack and fill pressures at each of the selected positions within the one or more mold cavities during the first injection cycle, establishing second axial positions for each of the valve pins (1p, 2p, 3p, 4p) relative to each of the respective gates (1g, 2g, 3g, 4g) that are determined according to an algorithm that determines an adjustment in the axial positioning of each of the valve pins relative to their respective gates that will effect an increase or decrease in the fill and pack pressures relative to the recorded fill and pack pressures that more closely approaches the selected target fill and pack pressures, injecting injection fluid on a successive injection cycle through each of the gates and controlling the actuators (1a, 2a, 3a, 4a) corresponding to each gate (1g, 2g, 3g, 4g) to adjust positioning of the valve pins (1p, 2p, 3p, 4p) to the second axial positions for each of the valve pin that are determined according to the algorithm such that pressure or velocity of flow of injection fluid through the gates is adjusted to more closely approach the target fill and pack pressures for each of the selected positions within the one or more mold cavities.