Not very good news
Would be worth inspecting the damage to try to get an idea of the cause. You say it has big turbo and injectors so it will have been re-mapped.
Look for mechanical type damage, cracks or just general broken parts (eg the part of the piston that separates the rings) is more than likely excessive boost pressure.
Melting type damage or lots of pitting would usually suggest too much ignition timing and this tends to be concentrated round the plug area.
Once the piston is out your mechanic will be able to spot if anything out of the ordinary has been happening
Cylinders are suprisingly tough so unless its thrown a serious fit then that will probably be ok.
Also when the head is off check for signs of a damaged/bent conrod. When the crank is in a certain position all 4 pistons should be the same distance down the cylinder. If you've got any differences the rod is suspect.
Im not too familiar with the VAG 2.0 FSI but on some vehicles when messing with injectors its quite easy to nick a seal or pop them out leaving any excess fuel in the lines to spill into the cylinders. This then sits on top of the piston untill you turn it on the starter then the engine hydraulics causing damage. When swapping injectors it's always advisable to whip out all the plugs and give it a spin on the starter to clear any fuel that may have entered the cylinder.
Just a few ideas, hope you sort it
