Have a 2016 Envision 2.0L T, have come to find out it is not producing enough boost.

It drives good. I recall putting my Torque App on it and seeing 4.5 PSI of boost. Now I cant get it to boost past .5PSI. It drives great unless you really press the pedal down on a steep grade and it will throw a code saying it was under boosted. I can unhook the boost control solenoid and get up to 14PSI and then it throws an over boost code and goes into limp mode so I know the turbo is capable. My question is if I get this HP Tuner product will I be likely to diagnose and understand what could be the cause?