A note on fuel pressure: Boost pressure fights fuel pressure, but I don't know if the psi difference from a nitrous bottle is really a major issue -- all the power comes from adding a ton of extra oxygen to the mixture (much more than the in same quantity of ambient air!), but not so much through compression of the charge, meaning lower charge pressures, at least as I understand it (someone correct me here if I'm wrong).
Anyway, even if it causes a slight drop in pressure, it's really the increased oxygen concentration you have to worry about, and without adding more fuel you can run very, very lean.
Now, although the nitrous itself will cool the charge as it enters the IM (it's cold! The IM may feel frosty), but the benefits of the temp drop going in is at odds with the lean burn in-cylinder if fueling is insufficient. This may create hot spots on the piston crown and can cause flame kernels to flare along it, resulting in preigntion and knock... also, the greater pressure wave created during combustion can cause autoignition of the fuel, also resulting in detonation and knock (i.e., un-timed/unplanned combustion events -- engines don't generally like that).
Sooo... long story short, fuel pressure drops shouldn't really be the big issue to contend with (maybe for motors that run adjustable FPR's?). It's making sure your injectors can handle the fueling needs, tuning them to have increased duty cycles when spraying, and retarding ignition advance and using "colder" plugs, making you less prone to preignition events.
Actually, with enough of a pressure wave, you can crack a ringland without any detonation -- the force alone can break it on the compression stroke. I doubt you have to worry about that considering motors are holding together making tons of torque (although more gradually with turbines, whereas N2O hits full force all at once...)
And/or, like I said, a safety device that can shut it down/pull tons of timing at the first sign of knock or water/meth injection are also good additions.
Just spraying and playing, which lots of folks do, isn't a great idea for engine longevity, and although the motor may never have a problem during the course of your ownership, the second owner might wonder why s/he has spun a rod at < 100K...
Anyway, it sounds like you are doing a lot of research and planning rather than just bolting it on and hoping for the best, so you should be having fun (and safely) before you know it
