EEC-IV Operation

Fuel enrichment using adjustable fuel pressure regulator
The EEC reads its "base" injector pulsewidth "Duty Cycle" from a table, and then multiplies it by its the "load line" and then by "adaptive fuel control table" before it goes out to the injectors.

Load is a line plotted with VAF vs. engine flow efficiency, but it is also increased/decreased by certain amounts depending on air temperature and barometric pressure.

This adaptive fuel control table is being modified, but ONLY WHILE THE EEC IS IN CLOSED LOOP OPERATION, however that same table is used in open loop operation also, its just not being modified at the time. The adaptive fuel control table has lots of cells in both the RPM and load axis. By upping the fuel pressure the ECA will learn to lean out the low load parts of the adaptive fuel control table so it runs just like stock. At closed loop the ECA will edit the adaptive fuel control table to keep them close to stoichemetric even at high load. At WOT (open loop) the the higher fuel pressure will enable the injectors to deliver more fuel at higher than stock load. So yes, adding a adjustable fuel pressure regulator will add fuel, up to a point.

Startup fuel cut off
My sister designed some of the EEC-IV software. She looked in her reference material to see if the injectors are disabled during cranking at wide open throttle (WOT). A brief statement refers to doing this if the engine appears to be flooded. It confirms that the injectors are disabled when cranking at WOT.

She also noted that the throttle position sensor is designed to be automatically recalibrated based on its most recent excursion to what it thinks is WOT. That means that small changes in TPS accuracy should not effect the EEC-IV's ability to detect WOT.

VAF sizing
The stock Ford small VAF will work fine for 320 cfm of airflow. This is good for 220-230 hp at stock fuel pressure.

The large VAF is good for 360 CFM or 250-260hp, again stock fuel pressure.

The stock 35 lbs injectors are good for 260-270hp, some people have made more power but it is lean at higher levels. At near stock boost levels most people will never lean out the motor. Adding more fuel pressure tends to richen up the whole curve, this is not good. If you are maxing out the VAF you need a bigger VAF.