Need help, posted problem before but still not fixed

coming up as

17965 Charge Pressure Contr. Positive Deviation

Brought to dealer and they want to replace turbo , but they are too lazy to try and fix it, any one no what to do, have changed air flow meter and N75 valve,

Turbo cuts out at high revs and comes back in for a little while when ignition is switched on and off, fine around town just when i put the boot down

If anyone can help, please post

Cheers

Dave

Anybody any ideas? Try the TDIClub here, Dave, if you don't get any feedback here.