Joined a bit late in the game here. I'm suffering similar problems
Fault code - boost pressure between turbo and throttle control (check D.V.)
Goes into limp mode as and when it sees fit until it gives up the ghost completely, stays in limp mode and eventually throws the engine management light
Visit my mate with VAG-COM, clear the fault, back to the same behaviour
I've replaced the MAP sensor, MAF sensor, N75, coolant temp & recirculation valve so far...
The problem started with a boost control valve error that transpired to be a split in the vaccuum pipe that runs under the inlet manifold
It ran fine for ages after we fixed the split pipe
Now we have the pressure being lost code
Mine's totally standard and the limp mode isnt that apparent when you watch the speedo. You can definitely feel it though.
Not sure if its related, saw something in the thread about a pipe under sump guard and I know occasionally when I hit a deep puddle it runs like a dog for a couple of minutes.
I just want it to be back to how it used to be. Do I just have to bow to the 80K rule?