and 725 injectors are WAAAAY to big for stock internals and you only need a bigger map sensor to run more than 12 (im pretty sure) psi which is more than enough to do a decent stock internals build. as far as widebands go, AEM's digital one is 180 shipped from most sites (the club integra store has em!!!) and are the way to go in my opinion (i dont have one for sale so I can prove its unbiased opinion lol)
lol until you get up better than a 1000cc you cant really have too much injector. its all in the tune. its better to have too much injector than have to max one out. and i know he wont have that issue with a 440 or 550, but its not going to hurt anything. and yea thats right about the map sensor, but hes shooting for 300whp which is going to take more boost that that
as for the tune you can let xenocron know all the details of your setup and they will send you a basemap tune for it, but your still going to have to learn to tune, which isnt hard, or take it somewhere and have it tuned. and thats crucial, there is no replacement for a good tune, its a must