On topic, my opinion, call a reputed workshop (STechnic, Maximum Motosport, RaceTorque, Evoultion R) and ask their professional opinion.

What some of the others are saying (jokes aside) is not just heresay...it is based on many GD WRX owners' previous experiences (around the globe, not just here).

Running higher boost levels on a GD model WRX (which yours is being an MY02) IS unsafe without a tune. The GD models are very sensitive to any changes in air/fuel...as in, even bolting a simple short ram/cold air intake will cause problems eventually, leave alone something like solely upping the boost).

My 2c.