It probably has a 60trim wheel on it which pritty much keeps your boost at 15psi all the way till redline vs dieing off at like 5k rpm.
I am not sure what the difference between GEN I 3s and the GEN II are but from what i understand if the stock injectors are the same as the GENII (440cc) then the supra turbo will not have enough guts to lean out the stock fuel system. I may be wrong i will let chris come in on this one becuase i am still learning about the 3s Generatoins
As far as opening your engine up...no..you wont need to unless something si wrong inside, people have pushed over 400whp without opening the engine up so you have noting to worry about.
Fuel pump, injectors, and the smt6/7 is the base for fuel upgrades