Boost pressure has no bearing on what N20 jet you will use.
If you had a seperate fyel setup just for the nitrous I would just set the fuel pressure at 43.5
As long as you use the right fuel jet for the fule pressure you are running then the fuel pressure you choose isnt that important.
I say 43.5 because most kits will reccomend cetain jets based on you using 43.5psi fuel pressure.