Actually in regards to the fuel system (rails, injectors, regulator, pump), when i got pulled over (booze bus blitz but they made me go up on the grass) I asked about it and he told me its not illegal to modify the fuel setup but it is illegal if it alters emmisions (although extra injectors are illegal). So its not a road worthy issue its an epa issue. So if you do get pulled up and let go, expect that you will most likely get a letter from the epa.
Cos it is a GTR, you are still only allowed to upgrade either to pods or upgrade the cooler. If the cooler is aftermarket, you have to prove that it is the same dimensions as the standard one in order to have both intake mods.