dont fit a manual boost controller to a remapped car its pointless!! i agree with the others get vagcom on it i expect it will have codes.
also do logs of requested vs actual boost. that will give you an indication of a boost leak.
def sounds like a hardware
problem. also if its ok and doesnt go into limp mode under full boost then its not the map
also what dv are you running? dv with 2 stiff a spring or not stiff enough can cause car to go into limp mode.
you will get an error code saying "pressure drop check dv" (cant remember the exact code) sometimes this code sends car into limp mode and sometimes it doesnt!