Just a thought about fuel pressure. Going from 43 to 48 psi makes much less diference than you think. It would make the N2O mixture 5% rich, and the overall mixture going to the motor around 2% rich, not really enough to mkae that much of a difference.
Something I discovered while playing with the juice, if you want to increase your ET, spray as much as possible, as soon as possible, right off the line, if your tires and suspension can hold it. Spraying past the 1/8 mile has MUCH LESS
effect on the ET.
Increasing your spray in the last 200ft has a DRAMATIC efect on your MPH, though. I gained 5mph, from 115 to 120, by spraying through the traps, versus shutting down 100ft early!!!
Something else to consider, the higher the state of tune NA, the less effect the juice will have.
Good luck, and may the Nitrous Gods smile on you