My better half complained her wagon was throwing an overboost code and limp mode, but only when cruising at highway speed. No limp mode when she gave it an Italian tune up, but it didn't help either.
It has an OMI so you can't really see the actuator from up top, so I put it on ramps and took the skid plate off to run the VCDS boost control test. Actuator was not fully returning to the no boost position, turns out the circlip was missing and the rod was at an angle and jamming against the turbo, preventing it from going all the way up.
It was guutnstuck so I had to unbolt the actuator to get the rod back in position, then rummage through all my junk drawers looking for a suitable circlip. No luck so I made one from a scrap of steel, tested it on a spare turbo and it seemed like it might work.
Predictably, I dropped the macgyver clip trying to install it. It fell on the top of the subframe so I reached up to find it by feel - and came up with the original circlip! What are the odds?!
The original circlip didn't fit tightly, probably why it fell off, but seems to be secure after a little bending.