Best of luck with it bud, sounds like a lot of boring legal stuff to do.
With the engine it sounds like they have either wiped the ring pack on the pistons which can be confirmed with a compression test, damaged the turbocharger reducing air flow required for correct combustion mix, but this would have a high pitch scream and the turbo oil would be black. Or if you are lucky simply wiped the injectors causing inconsistent atomization of the fuel. Or if you are really unlucky all three!!
I will have my fingers crossed.