Hi, Sounds like you have a air leak, check all connections from the turbo to the intercooler and from there to the inlet side of the engine (to include throttle body)
Maybe when you fitted the new turbo you have not connected the pipe work correctly, you say the actuator you have was working ok before, -31 is approx 8 psi, when you pull on it does it it feel like its ok, not to soft, if the turbo linkcage is closed as it should be when you connect the actuator to it, and you have some pre-load wound into it, you should have some boost, more than 0.2bar =2.9psi. i take it the airfilter is not clogged, you have no air leaks as mentioned above and you have no exhaust restrictions, maybe the penny washer @ the wastegate is worn not seating properly all this assuming the new turbo has been tested and is good. what was the problem with the old turbo. regarding the boost, take out the bleed valve i take it by what you say its not the factory valve, with the valve taken out connect the compressor pipe staight to the actuator & check to see what the max boost pressure is,
Regards Dave R.