Reason you have such low boost is due to the free flowing exhaust. The less restriction you have in the exhaust the less boost the car will register. If you installed a factory exhaust with cats you would pick up some boost.
People forget the pressure is not the metric the engine cares about, it's all about air flow.
Also you probably picked up a decent amount of power, you just can't compare the runs from few months ago because the air conditions have changed.
You should of dynoed before and after on same day to verify gains.