Code 16618 and P0236

Had my 06 Passat 2.0TDI in for diagnostic today after problems with car going into limp mode at higher revs in 4th or 5th gear.

The codes shown were 16618 (overboosting)as well as P0236 and 01314. I have recently had the Turbo replaced and the timing belt changed. Various tests conducted on pipes etc but i'm told that next step is to remove and asses the turbo unit.

Keen to here any views on what might be causing this. As stated the turbo was recently replaced with a reconditioned unit, so reluctant to start removing it again and hoping could return under warranty. The original turbo failed as bearing collapsed. Car has 88k miles.