The pink is supposed to be at a full 12V. With the fuse out, there's no current flow, so a high resistance somewhere in the circuit isn't going to drop any voltage and that's why it looks OK.
See if you can monitor the fuse voltage with it installed, such as with an add-a-tap gadget.
The high side of the fuse is actually connected to the RUN/START bus coming from the ignition switch, not straight to the 12V battery bus, but I bet you found that out already.
You might also have a high resistance connection from the coil side of the fuse to the injectors. There's some redundancy in the wiring to the injectors (three connector pins in the harness at the fuse block, each one feeding two injectors). All I can think of is a bad fuse socket right now. OK with no load, but can't run an injector without dropping voltage down to what you measured. A shorted coil or wiring harness would blow the fuse.