Over the weekend my Mrs went down the South Coast to meet friends whilst I was out of town, and on the drive the vehicle went into "limp mode" after there was a "ding" and the coil light started flashing. When she stopped, turned the engine off, then started it again it worked fine... for a while, and then did it again.

So when I got home last night I plugged in my VCDS cable and did a scan. BTW, it's a 2010 Tiguan TDI.
Code:
Wednesday,21,November,2018,19:04:52:57103
VCDS Version: Release 18.9.0 (x64) Running on Windows 10 x64
Ross-Tech: Home

                Address 01: Engine       Labels: 03L-906-022-CBA.clb
Control Module Part Number: 03L 906 022 G    HW: 03L 906 022 G
  Component and/or Version: R4 2,0L EDC G000AG  3396
           Software Coding: 0000175
            Work Shop Code: WSC 01649 959 95524
                      VCID: 2977073980262D02A2-807C
1 Fault Found:
                Address 01: Engine       Labels: 03L-906-022-CBA.clb
000665 - Boost Pressure Regulation 
               P0299 - 000 - Control Range Not Reached - Intermittent - MIL ON
             Freeze Frame:
                    Fault Status: 10100000
                    Fault Priority: 2
                    Fault Frequency: 2
                    Reset counter: 255
                    Mileage: 181063 km
                    Time Indication: 0
                    Date: 2000.00.00
                    Time: 13:14:27

                Address 01: Engine       Labels: 03L-906-022-CBA.clb
000665 - Boost Pressure Regulation 
               P0299 - 000 - Control Range Not Reached - Intermittent - MIL ON
             Freeze Frame:
                    RPM: 2208 /min
                    Speed: 98.0 km/h
                    Load: 71.8 %
                    Absolute Pres.: 2346.0 mbar
                    Absolute Pres.: 1468.8 mbar
                    Lambda: 98.6 %
                    Lambda: 33.9 %


Readiness: 1 1 0 0 0
I reset the fault code, and took a test drive. The engine pulled file, clearly coming into boost and reving to 4000rpm quite easily. But after sustaining 100km/h or so for a couple of km's the fault popped up again and the car went into limp mode again. Reset the code, and it was fine again until I sustained speed again.

I thought it might have something to do with the MAF sensor as apparently they're known to get dodgy, so I unplugged it to test after reading this thread - Maf 101 - TDIClub Forums
When I turned the key it immediately threw a code coz of the "missing MAF sensor" but it drove fine. Pulled like normal and was clearly in boost, but on the same test loop I was doing it went limp again.

Because the car ran fine with the MAF unplugged I'm thinking it's not the MAF sensor... so I plugged it in again. Testing again this morning I got the code again. There is no obvious sound which would indicate a split in one of the boost hoses, but I have to admit to not knowing what I'm listening for. I can't say there's an obvious "turbo rattle" either, but again, I am not sure what I am listening for.

I'm fearing my turbo is giving up the ghost, but I'd like to exhaust any other avenue I can before attacking it. It looks like it'll be a nightmare to get to, and from the sounds of it they are friggin' expensive. Even getting to the boost hoses going down to the intercooler is difficult, but the hose I can get to I have felt and there is no obvious splits in the hoses or loose connections.

Any suggestions?