You all need to learn not to trust your fuel gauge!!! .. my MY96 always says it's nearly empty at 420-450km's .. but I fill it up and only get 45l in or so .. 15l in the tank ..
I get 530km's up to 550 from a 60l tank of U98 ... 13psi/3 turbo back/cold air duct to standard airbox in mostly urban driving and driving it reasonably spiritedly.
Ran a 13.9 the other night .. I think it can do about 13.7 with a better launch though.