Charge air pressure control deviation 2884

[struggling]

New to this, and Minis.

Searched the site but not found anything to help me, really struggling now.

Its a 2006 Mini Cooper S turbo with the N14 second generation engine.

Problem: pulling out to overtake on a motorway and goes into limp home and code 2884 Charge air pressure control deviation comes up. I can make the fault happen once cleared by accellerating in high gear from low revs.

I have access to Dehphi diagnostic software so can plug in and view data live and erase the codes.
OK so heres whats been done so far:
ECU updated software
New boost pressure sensor
New map / pressure sensor
Overun bypass valve removed and checked, and checked for operation with Delphi software tool and componant activation method.
Pressure tested intercooler and pipework (made blanks just before throttle body and out of turbo)
Checked wastgate actuator pipes for leaks under pressure and vaccuum - OK
Checked vaccuum pump working - ok
Checked the operation of the wasgate actuator by using a vaccuum gauge, nice and smooth in operation.

The only thng not yet done is to remove the Cat and check the wastegate butterfly valve.

Driving normally (not thrashing or wanting boost in high gear) the car drives lovely, no problems at all.

With the delphi kit conected and reading live data of the boost the fault is not overboost, the fault can be generated at various levels of boost dependant on what gear you are driving in.

I have scoured the internet for all known faults but just losing the plot with it now.

I have had a trained BMW teccy look at the car with BMW's help and they seem to be struggling just giving the code 2884 general check list which i have covered.

I cannot justify the £115 per hour BMW charge.

Anyone had similar problem or suggest something i have not checked??

PLEASEEEEEEEEE

Sorry forgot to add the fault does not reset when the ignition is turned off and on. The 'Limp' home function just has the effect of no turbo pressure and drives like a non turbo car

[struggling]

Thanks for help suggestions people.

For info had Quantum tuning map done and so far 100 miles in no problems