If I have a guess :D what in my mind is..
Maybe he uses a R75 pump from 2.2 hdi because it can deliver more stable fuel at higher rpm and higher rail pressure and as I heard it more or less plug and play for a 90 Hp Hdi. :)
Turbo I think around 270 Hp he need a big airflow assuming a GTB2260 or bigger one. Pressure maybe higher than 2.0 bar so if it Map based it require a (relative)3.0 bar mapsensor and big FMIC. Straight throught exhaust about 70mm I think basic :lol:

Regarding the Fuel system there could be an upgraded 1800 Bar rail sensor as in upper comments he talked about.
And may other little modifications which helps to maintain this huge power and much torque :D For example I heard about HDis the diesel filter housing can also be a bottleneck to achieve some huge gains.
Maybe he also can change the engine internals..and maybe swapped engine head to 16v for betteg VE but I don't know.. :)

So these are my fictions :lol: about how to achieve above 200HP but I'm curious about the real mods :D

gtb 2260 its big enough for 270 hp ,but you dont forget best inyectors.... to make the injection time shorter