I honestly don't think that's an issue, sounds like your TCS won't work but most people would pull the fuse anyway, in fact check the TCS fuse, I bet someone has already pulled it to do burnouts as it sounds like some loser was the previous owner with the gay atmo BOV and everything else being broken.
Drive it now and see what your economy is like, and tell us how do you drive it, do you drive it with a few boosts now and then, or do you drive it like you are on a racetrack, as if it is the later it would explain the 200kms to a tank.
Also does it blow much black smoke? Get someone to drive behind you and take off hard in 1st and second.