Found an interesting link describing what pop pressure differences do for performance.
Injector_sizes
"Then there is POP Pressure of the injector or nozzle to deal with. What POP
pressure do you run. Well that all depends on if it is a 12v or a 24v. This does not
apply the Common Rail Cummins as they are EFI not mechanical injectors.
Using the 24v as the example, there is a range on the POP Pressure. This range, ranges from 3800 psi (262 Bar) to as high as 4500 psi (310 Bar). Alot of companies say not go below 260 Bar (3770 psi).
POP Pressure has an effect on timing, smoke and atomization. Plus high POP Pressures have an effect on the fuel being sprayed into the cylinder under high boost pressures. Also, every 10 Bars = 1 degree of timing. 1 Bar = 14.5 psi and 10 Bars = 145 psi. So added 10 Bars of pressure REDUCES the timing by 1 degree and lowering the pressure by 10 Bars ADDS 1 degree of timing. But lower the BAR pop pressure also has an effect on smoke, more smoke.
Rule of thumb is higher POP Pressures help with street driven trucks. Lower smoke, better throttle responce, better drivability and a little lower egt's."