I'm not sure about your boost problem, sticking wastegate actuator?, but you may have another problem - possibly the GGR module is wrong for your setup.

From memory, the GGR270 chip ran the injectors to their limit and to get around this with the GG305 chip the fuel pressure regulator was changed to up the fuel pressure. I think the standard injectors are rated at 311cc/min and by putting in 500cc/min injectors (which the ecu doesn't know are there) there is going to be major overfuelling problems. At idle the closed loop system will compensate to some degree by reducing injector pulsewidth to try to get 14.64:1 air fuel ratio and the results of this compensation will also be used at open loop. But not enough to stop the problem.

Is your chip a special by GGR or the normal GGR305?