The engine starts creating enough exhaust force to spool up the turbo right around or above 2000 rpm. At around 5252 rpm, the engine torque crosses with horsepower, so in theory you should be able to keep the car accelerating up to that point if you really need to get moving fast for a tricky merge. However, your car is programmed to start dumping boost pressure if it starts to exceed... 19 psi, I think. This is to avoid damaging the intake from too much pressure. So at some point (probably 4500 rpm-ish) your car will be at max boost and will not push harder.
Essentially, GM designed a few failsafes into the car to keep you from blowing up the turbo. If you ever decide to get an aftermarket tune... then you've got a whole other ball game.
P.S. This car does not respond well to wide open throttle clutch dumping. The best way to achieve a fast and consistent start is to roll the throttle on smoothly. This is even more important since our car has a dual-mass flywheel, which needs a smooth pressure increase to prevent lurching in the drivetrain.
