I use NOS here, but it is entirely up to you. This is an area where your own line of reasoning comes to play. I used a NOS 90 degree nitrous nozzle. I did this so that I could aim the injector INTO the air stream for better atomization. It's far enough from the TB that I don't think turbulence is a problem.
Atomization is key, that's the reason for the high psi pump.
NOS has straight on nozzles too if you disagree with my reasoning. You'll also need a nut to mount the nozzle. The nozzle won't thread all the way in but it only needs to be flush with the nut seat. By a few of them, for you will be tuning. Try anything between .025 and .035 flare type jets.