Hey Jonah - Just to eliminate a potential relay problem- have you pulled the Computer power relay (XVI) and inserted a 3 way jumper to connect relay socket pins 30 and the (2) 87 and 87 pins together ?
Also Stepson made some good suggestions on cleaning your injectors. Although sending the injectors out to be professionally cleaned is best - here is also a Utube demo- showing a pretty good stand-up/sit-down home grown procedure.
Be careful to only apply + 12 volt power to the injector coil for very short bursts so they don't over heat. The normal pulse length is in milli-seconds.
Many years ago I bought a match box sized hand held digital injector pulser that allows me several selectable pulse rates for troubleshooting and cleaning. This rig is still reasonably priced and has paid for itself many times over.
https://www.youtube.com/watch?v=rUUgR94drxg
Good Luck - Michael