Sounds like you aren't getting overboost. On a standard engine the boost will go up to the solid block whilst driving normally. If you put the pedal to the floor you should get eight seconds of overboost when the needle goes into the dashed area just below the red. If you keep it floored the needle will drop back to the solid block after 8 secs.

Overboost is the first thing to go if your ECU logs a fault - then you'll only go to the top of the solid block and will be well down on power. This will also happen if someone disconnects the AMAL valve or bypasses it without adjusting the actuator to compensate once they have fitted a chip.