The BEST I ever got was 450.. that was driving at ~ 120km per hour for the whole tank (from brisbane to melbourne)...
the WORST I ever got was 140km... that was some very hard driving
After changing my fuel filter, I am now getting about 400 a tank, which is fanging it for the 1st half, then realising i have no money, so taking it easy on the 2nd half..
Btw, my car runs 8psi to 4500rpm and 10psi over that.. has pod, ecu and zorst (173rwkw). It also has a higher ratio diff, which I would think would be the main factor in my shit fuel economy (100km/h in 5th is 3100rpm.. compared to std of 2700 rpm)
edit: thats using BP Ultimate (always) and I usually fill about 55-60l.