first is there a mil light on. if not check and listen if there is a high pitch wine coming from your fuel pump. If there is no wine from the pump and no mil light try scaning the car with generic scan tool if no comunication is possable then ECM could be the problem.
If you can read ECM check turbo diverter valve for suck open valve or turbo line for tears or leaks ususally by the boot goin into the air box down by the turbo wastegate valve.

 

So. Update:

I disassembled all electronics and all component on the air intake, including the thingy (dont know the english name) with the gas lever. I heated my garage, and let everything dry completely up, blew air on contacts and electrical connection-spray.

I found a whole lot of water in the air-intake, and a lot of it seemed to have moved further into the engine. Cleaned everything up, and now: Runs like nothing happened!

PHEW.