sorry i probaly worded that wrong, if your in 3rd gear and doing 30 mph, and low down in the revs, put your foot down, as the car picks up speed and the turbo spinns up, it will come on boost then just after around 4500 rpm it will cut
it seems like the actuator needs adjusting to drop the boost
it boosts at 20psi and holds at 16psi, is this the spring gone week