Nice description on technosquare about how the ECU adapts. The do a flashing service which alters the parameters so allows for mods. http://www.technosquareinc.com/nissanintro.htm
You wont see 100% throttle on even a stock 350z. Its not tuned to use 100% throttle as far as I can tell, it doesnt get anywhere near it, and it makes perfect sense to put a part in that is working well within its limits so thats what I'd expect. The throttle can flow more air than the engine needs, so it never needs to open 100% and doing so wouldnt make any difference as the engine doesnt want the extra air. With a remap, it'll use the extra air, but I doubt the throttle needs to be open 100% then either, but it will