If you going for an rb then go for at least an rb25 the rb20 struggles to idle they are that gutless
Fuel injection is more than just for emissions, remember they made carbs for emissions as well.
The good thing about fuel injection is you can have it all. nice and economical off throttle and then the delivery when you hit the loud pedal.
Sure you can get a carby engine to drive nice but your not going to get the same results you can get from efi, no way