L322 Manifold BOOST SENSOR FAULT

Range Rover L322 3.0 (04 plate 2005 later modle)
Can anyone help me?
The air manifold boost sensor was showing up on diagnostics.
The mechs reconnected it but found that the turbo started to whine as it seem to be overboosting ( I think they said the pressure increased 7.0psi).
They said that the boost sensor appears to be working.
The car had a new turbo fitted prior to us buying it so this plug has been off since we bought it over a year ago.
It pulls very well and the mechs have checked the turbo and said it is OK.
they also cleaned the turbo dump valve.
I cannot understand how the air pressure is increasing as I was under the impression that the boost sensor via the ECU altered the fuel setting.
Is their another dump valve?
It was also suggested that the car may have been mapped/chipped and maybe the boost sensor was left off.
Can anyone shed any light on this one?
thanks in advance
Al

The MAP sensor was disconnected to avoid over boosting by the previous owner and would only run basic settings

you plugged it back in and hey presto...over boost.

you need to get it re-set/set lower to avoid over boosting all the time,gong into limp mode and killing the turbo.

Make sure the crank case breather valve has been replaced as this usualyblocks causing the turbo to fail also mite be worth seeing if it has been chipped by the previous owner

How does it overboost?
How do you get the settings changed?
thanks
Alan