2007 1.4tsi boost problems ***HELP***

for a number of months now i have been trying to fix a 2007 golf 1.4tsi engine code blg, the problem is with the switch over from supercharger to turbo. we have tried a number of things to sort the problem but so far no joy.
to start with the fault codes we had were

Address 01: Engine Labels: 03C-906-032-BLG.lbl
Control Module Part Number: 03C 906 032 A HW: 03C 906 032
Component and/or Version: MED17.5.1 9971
Software Coding: 0000072
Work Shop Code: WSC 00442 210 91419
VCID: 1B3E003BA33E
2 Faults Found:
008801 - Boost Pressure Control Valve (N249): Mechanical Malfunction
P2261 - 000 - - - Intermittent
Freeze Frame:
Fault Status: 00110000
Fault Priority: 0
Fault Frequency: 1
Mileage: 58824 km
Time Indication: 0
Date: 2000.00.00
Time: 16:04:25
Freeze Frame:
RPM: 2590 /min
Load: 26.7 %
Speed: 61.0 km/h
Temperature: 85.0°C
Temperature: 16.0°C
Absolute Pres.: 970.0 mbar
Voltage: 13.970 V
004261 - Position Sensor for Intake Air Regulating Flap: Signal too High
P10A5 - 000 - - - Intermittent
Freeze Frame:
Fault Status: 00100000
Fault Priority: 0
Fault Frequency: 1
Mileage: 58824 km
Time Indication: 0
Date: 2000.00.00
Time: 16:04:21
Freeze Frame:
RPM: 2737 /min
Load: 90.6 %
Speed: 53.0 km/h
Temperature: 85.0°C
Temperature: 18.0°C
Absolute Pres.: 970.0 mbar
Voltage: 13.589 V

the boost pressure control was cleared by replacing valve on side of turbo, we was left then with the position sensor for intake reg flap. we tried pcv on top of engine, both intake reg flaps but still no joy. then as the car was on its way back to try the clutch for supercharger it decided to blow a piston (cylinder 4).
to repair that we fitted a new piston, rings on all 4 cylinders, full set of shells on crank and con rods (not looking worn but pitted), timing chain, oil pick up pipe, gaskets and seals. now that the engine has been rebuilt we could continue to try and find the boost problem, so the supercharger clutch was fitted, and once again still boost problems. the position sensor flap fault has now gone but the boost prblem has not.

whilst out on another test drive a dtc was stored (misfire cylinder 4), we decided that we would replace injector number 4 as this could of helped in the destruction of the piston. now replaced we scaned before another test drive we have found a different fault
Address 01: Engine Labels: 03C-906-032-BLG.lbl
Part No SW: 03C 906 032 A HW: 03C 906 032
Component: MED17.5.1 9971
Revision: 96H06--- Serial number: VWZ7Z0F8011590
Coding: 0000072
Shop #: WSC 00442 210 91419
VCID: 1B3E003BDABEE11
1 Fault Found:
008196 - Intake Manifold Flap; Bank 1
P2004 - 000 - Stuck Open
Freeze Frame:
Fault Status: 01100000
Fault Priority: 0
Fault Frequency: 1
Mileage: 59890 km
Time Indication: 0
Date: 2000.00.00
Time: 09:26:33
Freeze Frame:
RPM: 821 /min
Load: 12.9 %
Speed: 0.0 km/h
Temperature: 51.0°C
Temperature: 8.0°C
Absolute Pres.: 980.0 mbar
Voltage: 14.224 V
Readiness: 0110 0101

stripped back down the flaps seem ok and move freely, the vac pipes seem ok as does the actuator. so we presumed it must be the potentiometer and fitted a new one, but still we have the intake manifold flap stuck open fault. (no visable fault as we can see the actuator moving)

we decided to take it out on a drive to see if it would clear itself, but still no joy.

so after all the problems and repairs we still have the boost problem but non of the original dtc's

the boost problem will only occur after driving for about 10 or 15 minutes. if the car is left idling for any length of time (even an hour) it will still take about 10 or 15 minutes of driving before the fault happens. the fault has been the same all the way through the repairs and changes of parts, the only thing that has changed is the fault codes.

can anyone please help, as i am runing out of options with this one now.

I have the same problem with my 2007 VW golf 1.4 tsi bns, what was for you the answer to the problem. Because we are also out of options. We have also changed different "ventil" parts. also the the sensor has no malfunction we checked it diffrent time`s. No leaking in vacuum system. Changed the bougies, etc. Still the same problem.

Hello,sir.
This problem is the same which I have faced for three month/ The problem was flap position sensor. You can not see p2015 error because your sensor electronic part is in working condition,but other side which is turned by flap rod may be in wrong position, or gets stuck after some turning period. You should remove that part ,check condition,if inside plastic shape can be turned easily,then turn it in 180degree. Then reinstall back and do diagnostic/ P2004 will be removed.