phunk

There are 3 typical ways to make more power per PSI.

-Colder Air
-Improving natural airflow through the entire system as a whole (often referred to as Volumetric Efficiency)
-Tuning

Tuning is sort of obvious. More efficient & optimized tuning will produce greater power output given the same quantity of air and fuel. Being on pump gas, I would take a guess that it is not tuned very aggressive.

Airflow is most likely where most of this is coming from. A turbo that flows better on the exhaust side will cause less restriction of airflow through the engine system as a whole, in the same fashion a better flowing exhaust system will; therefore lowering boost pressure at the same airflow. Airflow is airflow, boost is the measurement of how much the airflow through the engine is being restricted between the turbocharger compressors and the engine cylinders. If you increase airflow through the engine, such as a higher flowing exhaust (or higher flowing turbo hot-side), boost pressure will go lower even though the airflow (thus power) remain just as high. Although if you want to be technical, a wastegate is regulating boost pressure not airflow, so you would have to turn down the boost to keep the power the same after improving airflow through the engine.

Temperature is a small factor here, since lower boost means less heat generated through compression, translating to lower intake temps, denser air, greater power. So this is basically a compounding effect of a turbocharger that flows better on its hot side... I would guess making a rather minor contribution since we are only looking at a few psi difference.

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