I've had good experience with getting her going after stupid me forgot to turn the ball valve back on (that I installed on the Pre-Walbro pump/filter system) after a filter change, using this method (which I found in the shop manual, or on the TDR, forget where, but it works and without having to crack any injector nuts!): key to "run" position, you should hear FASS cycle for 10 seconds or so, you can also "jog" key to the start position and the FASS should run for 30 - 40 seconds or so, Foot down all the way on go pedal, crank engine over = not more than 30 seconds, if no start let it rest for 2 mins or more to allow starter lead wires to cool, foot down all the way on go pedal and crank again not more than 30 seconds. Repeat about 4, maybe 5 times and she should sputter to life, once it fires let off go pedal, it'll run rough until all injectors get fuel but smooth out and be good to go. Like I said, I found this procedure in shop manual or on TDR = I didn't make it up on my own "I ain't that creative" and it works. Hope this helps. If not you might have a fuel delivery from FASS to IJ pump. As asked by Wayne, "Do you have a Fuel psi gauge?" When you turn the key to "run" or "jog" it you should see some psi on the gauge unless the FASS isn't firing? Hope this helps.
If it was running fine before FASS install I'd bet the problem is with fuel delivery to the IJ and not elsewhere. Although if the IJ is old/weak it could have picked this "most inopportune time" to give up the ghost...
Please keep us posted and good luck!!!