Baben wrote:

tell em to check the pipe that runs from the intercooler into the engine intake - it tends to delaminate inside, and you lose a lot of pressure here. If you can see a bit of dirty oil at the ends of the pipe where it joins the intercooler and at the engine intake side, you have probly found your problem. Diagnostics probly won't pick it up, unless you get an intermittent "turbo overboost" or something like that. very common issue on the '06


Just read the bit about the problem starting after the service - make sure they plugged in the MAF sensor (although presumably this would be detected by diagnostics). Also check that the plastic air intake on the passenger side (if you are RHD) of the radiator has been properly pushed in. Although if this is the issue, you would have a lot of "surging" as well

hope this helps