if it's a highflow job with steel wheels, it's good for 18psi. But if your still running stock engine management, your going to run into all sorts of problems very quickly. I'd keep the boost low for now, pay someone to pull the turbo off and check that its a proper high flow job in good condition and find out what ECU you have.. if its aftermarket, take the car to a tuner and get em to tune it to run on 18psi. if its not aftermarket, thats probably your next upgrade. If your still running stock injectors, they are going to run out of puff at around 14 psi on the highflow as well. same with stock fuel pump..
in short, you need to get it checked out by someone in the know so you dont risk doing damage to the engine !