Unported 14b on free flowing exhaust is the problem. You could pull the turbo and port it to help alleviate creep as the first option. Essentially you port a groove down to the wastegate port to make as much exhaust gas hit the "wall" there and go 90* through the wastegate instead of flowing past it. Obviously you keep it smooth, but the port job takes more material out going down to the wastegate port. There are pictures on dsmtuners if you search for posts by "oldman" on the subject of porting. This is supposed to be the most effective way of eliminating creep.

Your second option is running 20 psi. What fuel, datalogging, and tuning capabilities do you have? You'd be surprised how much you can eke out of the stock setup if you have a logger and tune for it. We were able to run 21 psi on Kris's car on an Evo 16g and stock injectors by getting the fuel pressure regulator from a nonturbo 1g to bump fuel pressure to 47 psi base, leaning it out to the mid 11's at higher rpm where the duty cycles got too high, and compensating with reduced timing where necessary.