Hi have you had the fault memory checked are there any faults logged, also do you know if the diesel engine is a pump diesel with a variable vane turbo or does it have a VEP pump, if it is a pump diesel i would check all vacum pipes to ensure none have come adrift, if they are ok then i would check the boost pressure control valve for correct operation, if this is working ok then you will need to check the vacum valve and rod on the turbo and ensure it is operating correctly and not seizing up, pump diesel engines do suffer with turbo's so this can't be ruled out .
Hope this helps Chris
VW Technician
City & Guilds 1,2,3 Vw Master Tech cars&vans, VW Licence Tech
I was not able to finish the job before going to Peru, so it has to wait until I get back. I did find the EGR and intake were almost completely filled with crud. That helped some, but there must still be another problem. Thanks.
Dennis