You can't do it accurately and efficiently with a cable throttle car with just your foot in every gear.

You try and run 1 bar boost through the RPM range on your 2 bar capable car. You can only reduce boost by throttling the engine, but the throttled point of operation is constantly changing with RPM. Also a throttled engine is inefficient, you want the throttle as open as possible, along with the wastegate, for as long as possible.

Rick