I see, I thought all the 2V 4.6 mustangs used 19lb injectors. I know that the colors meant less in the later years. You might want to check the part number and make sure those are 21lb injectors. Be that as it may, the answer to your question is Bosch (and Ford) rate the flow of their injectors at 3 bar or 43.5 PSI.
Red '96 GT
PI heads and Intake, VT stage II's, Densecharger CAI, Pro-M 85mm MAF, Accufab 75mm TB, 1/2 " intake spacer, MSD Coil packs and wires, Mac Longtubes, Mac O/R H, Flowmasters, Steeda Tri-Ax, Spec Stage II clutch, AL flywheel, AL driveshaft, 3.73's, Max Speed Progressive rear springs, KYB AGX adjustable shocks/struts, GMS upper and lower rear control arms, UPR tubular K and coil overs, Cobra rear swaybar, full lenth subframes, Brembo cross-drilled and slotted rotors, high-temp Kevlar pads, poly bushings everywhere.