Compression/leakdown is a definite good step. Ad looks pretty good, he's even given the info for who built/tuned the car, which is a rarity. Pretty sure that is a pretty nice turbo; I do think that the mod list is not complete as I think there should be more supporting mods, although the guys who know more than me can chip in with what that turbo would require.
Edit: Just noticed that he says that the list is not complete and that you can contact him for the full list.
My only question would be: why's he selling if he loves it so much?