-When buying the HV3 High velocity intake insert off ZZP why would i need the L36 upper intake (+$90)

-When buying the High Velocity Throttle Body for the L36 is my car a stage 1 or stage 2 and what would i do about a core change

-Would I need to purchase any supporting mods for these items along those lines if i get the er rockers the only supporting mod needed is the aftermarket springs?

ZZ Performance
ZZ Performance

Thanks,
Bobby