2001 Passat 1.9 tdi with an intermitant boost fault. The car has been driving great for some time. Having an 80,000 mile service including a cam belt change last week the car was better than ever. The car would boost as normal for a 5-10 mile drive then suddenly nothing, no boost. Stop the car, turn off, restart, all normal again for a few miles.
I've checked the hoses around the turbo/intercooler and various vacuum pipes, but nothing amiss.
Yesterday, took the car back to the garage that serviced the car to have the fault codes checked, this is what they reported: CODE 17965 TURBOCHARGER PRESSURE CONTROL LIMIT EXCEEDED INTERMITANT FAULT.

What does this mean? Been told it maybe a holed/split pipe, but i've checked these!
HELP! PLEASE OFFER ME SOME ADVISE.