I have to agree, the only way to get extra boost safely is to remap the car. In theory the ECU will read the boost pressure with the MAP sensor and adjust the fuelling to match, but by using an after-market boost controller you are bypassing the boost limit so there is a good change you will just confuse things. Also, as Matt said, you will have no way on knowing if the extra boost is causing pre-detonation, and that can cause huge damage.