It *could* be anything. But maybe you will get lucky.
I've had the symptoms you describe three times on my 07.
First time at around 35000 miles, "Wastegate Controller valve" or similar name replaced under warranty. I don't recall if the name was Boost, Turbo, Wastegate - it was something like that and did eventually throw a code.
Second time around 42000 miles, similar initial symptoms, followed a few days into it with a really nasty metal on metal growl at low speed. Complete new turbo replaced under warranty.
Third time at 48000 miles, but out of warranty for time. Thought I'd look for a part number on the wastegate controller since I knew the turbo was OK and I couldn't find the part in a diagram. The part in question is a small black sensor on the front lower part of the turbo inlet. Two vacuum hoses on the top and one plastic covered wiring harness connector (small with two wires) leading to the front of the vehicle. As I was checking it I realized the connector plug (which hangs vertically) was about 1/4 inch out of the sensor. Push up, clear code, no problems for a day or two. Repeat for rest of week as I was busy at work. When I looked at the plug, the retaining clip was partially broken off. Not sure if it happened at the dealer or was always that way (may not have needed the first sensor?). Employed two zip ties and it has been trouble free for the last 20K miles.
Hopefully it's just the sensor or connector and not a turbo problem.
Good luck.