I think a boost-a-pump is the answer.
I'm going to get a dyno done somewhere that can data log injector usage before adding a lower +4 lb pulley and stock upper to see if I must add the boost a pump.
I looked at a few calculators, all gave different figures...

 

I use this one Confirm your dyno results with easy and simple calculations
and had asked about a boost a pump, their response was that you have to be carefull because increasing pressures can result in increased opening time of the injector effectively lowering its usefull duty cycle, or something to that effect..I was bordeline to begin with and running a 750cc inj kept me borderline with increased hp/boost. so just went to a 1000cc injector. I guess at this point you would just have to know where your duty cycle is on what youre running

 

what iv been told, is to much fuel pressure can slow the needle movement when closing , and it can upset the injector characteristics, possibly cause a phenomena that locks the injector 1/2 open and 1/2 closed , engine instantly runs lean, and puff the magic dragon!

it can vary in % all over the map.

YES that could ruin the day, when you at full boost, and a lot of advance! and just when you are pulling ahead of that guy next to you, DARN.

 

You don't want to hear what's my fuel pressure It's HIGH.

 

Lucky for me my car came equipped with a fuel pressure regulator and a fuel return line. The later years returnless systems may be better in retaining octane and such, but this is what the year 2000 Jag Gods gave me to work with.

I think the theory is that one of the advantages of the boost a pump is that it helps maintain pressure / prevent it from dropping on the high end.

I won't know for sure until I get the results of a data logging dyno, but I expect that with all of my mods that move so much more air, I will be outside of the parameters that the stock fuel delivery system was designed for and that the boost a pump can bridge the gap.

At that point, I would rather take my chances with rather than without the extra fuel supply.

 

You are now running a twin screw, right? What is your boost and what is your fuel pressure set to??

 

"Thanks" for the Walbro and Kinsler. Stable in 1PSI range from idle to 6000rpm.

 

A fuel injector is basically a solenoid valve that opens against the fuel pressure. They also have a spring to make sure the valves close completely when switched off. If you keep increasing the fuel pressure you can get to a point where the force of the spring + pressure is more than the coil can push against and the valve can't open far enough, or doesn't open at all.

The valves are usually calibrated to 3bar (40psi-ish) but Jaguar seems to run them at around a 60psi differential to manifold pressure.

Fuel pressure is one adjustment knob but you do need to be a little careful with it.