the utec's closed loop boost is a strange duck. it works PRETTY well, but not nearly as accurately as a more advanced system, such as an apexi avcr, or the oem ecu. basically it DOES use feedback to alter the duty cycle of the wastegate solenoid in order to actually target a particular MAP. unfortunately the numbers are mostly unitless.. you don't just type in 14psi and have it hit it.
if you haven't done so already, download mick the ginge's guide to utec tuning which will help you out a bit.