FWIW, turbochargers don't "make" boost.
And therefore bigger turbos don't "make" more boost than smaller ones. In fact, it's just the opposite. For any given rpm and fuel (drive) a smaller turbo will make more boost than a larger one.
With respect to turbochargers, engine power is a factor of:
Intake Air Pressure
-More pressure = more air for any given temp
Intake Air Temperature
-Less temperature = more air for any given pressure
Exhaust Drive Pressure
-Less drive pressure = more torque output for any given boost/cylinder pressure
A boost gauge is only a pressure gauge. It tells you nothing about temperature or exhaust drive.
When a larger turbocharger is fitted to an engine, and nothing else is changed (Ex: no more fuel, and no more rpm)
Boost will drop.
Intake air temp will drop more.
Exhaust drive pressure will drop.
Since the intake air temp drops so much it offsets the loss in pressure (boost) and the net effect is actually more incoming air even at the lower pressure, or at the very least, the same amount of air (if the charger is not horrably oversized).
However, the reduction in exhaust gas drive will allow you to produce more torque with even the same intake air pressure/volume flow.
The end result is more airflow from less pressure due to decreased air temperature, and more torque because of a drop in drive pressure that robs away engine torque.
The result is more torque at any rpm.....or more power.
But if you stare at the boost gauge blind to all else.....you might be left feeling shorted.
