As Ian I thing it sounds like the "Lectron" valve does't work. But I would'nt advice to remove it!! As this has been made to raise the boost presure with a better control than the wastgaste can do..
There is no overboost sensor the map sensor tell the ECU the boost presure and the ecu controle the lectron valve.
It looks like a relai inside you have a coil which when activate open a valve to release the presure from the wastgate actuator so he doesn't open a until the ecu wants to!
if it doesn't work (ECU safety, damaged loom or lectron valve) the presure remain the one preseted in the actuator about 1bar...