No that isn't the stock motor only later model 32 gtst's had the silver top NICS Rb20, it is a good thing though as it is better than the red top ECCS Rb20 which is the stock motor for the car. The silver top has bb turbo and rated at a bit more power.
As for potential Rb20s are good for stage 1 mods like exhaust, bit of boost, ECU, gives about 160-170rwkw.
Turbo, intercooler, fuel pump, AFM, injectors gives 200+kw but they lack torque and people usually dont bother and dump them for rb25s