Thats some nasty hack manual swap to still have all the auto solenoids and the TCU
The heat damage is not surprising - its the same sort of issue Martin had with his RS8, due to the engine bay being smaller because of the bulkier superstructure. Less airflow means the heat stays put. It would probably need everything in the exhaust flow to be ceramic coated and then well shielded back there to stop cooking everything.
Annoying that the only pic of the turbos is too blurred to see anything - it would have been interesting to see those since it's still using the original manifolds rather than the RS6 ones.
The 3.3 TDI had its turbos back there too, but diesels burn cooler than petrols (stock ones anyway) plus they had a lot of heat shielding.