Using the 95 computer in your 93 truck im sure you had to do some wiring to get to work. The OBDI port under the hood should still work. Im not sure how you got it wired up or what needed to be done.
Fuel pressure can be tapped off the fuel rail. I have a harbor freight test kit and it leaks on every vehicle I used it on. So i would avoid buying that. Check with your local parts store that loan tools. You may need to fab an extension hose and run it to a place you can read it. This would be very temporary. Option 2 would be an aftermarket fuel pressure gauge. They can be a tad expensive and really unnecessary if your not running boost or N2O
Cheapest digital/electric sender gauge I found.
Cyberdyne Gauges A012E351Y - Cyberdyne Gauges Digital Blue Ice Gauges - Overview - SummitRacing.com
BBK Performance 1617 - BBK Fuel Pressure Gauges - Overview - SummitRacing.com
If you haven't changed the fuel filter in the last year that would be my first step.
99 x-cab 4x4 4.0l auto
mods, cranked t-bars, silencer delete, k&n drop in, Rebuilt trans ,Trans Go stage 3 shift kit, 3200stall Fuddle Racing Torque Converter,
VANIR 63mm TB, Roush split rear exit exhuast, E-Fan, JBA Headers
Auto up/down both windows, OHC, EATC (soon to be modded)
03 Crown Victoria Police Interceptor