As far as performance adders, carbies are like turbos...the benefit gained is equal to the engine's potential.

With the right cam, more airflow is required. More airflow means more air/petrol which means bigger carb is required.

Twin SUs/webers/solex/dellortos can generally gain 10-20% more power over a stock carby on a standard engine.

It's not all fun, twin carbies need to be kept matched and in-tune. This is something that needs to be checked a couple of times per year.

Multipoint EFI has all the benefits of 1 carby throat per cylinder, but with none of the drawbacks..except expense maybe

Chris