Hey Grolscchie
10l/100km wouldn't be too bad for a 4WD atuo wagon (I had a T4 Primera auto - it could suck down a nasty 15l/100km when pushed hard, the best I ever got was 8l/100km.
If you know someone with a timing light (or better still a mechanic friend who would swap 1/2 hour of their time for a dozen beers) you should check you ignition timing. Not too sure what it should be on the legnum, many cars have a specification on a sticker on the bonnet (look at underside when you have bonnet up).
Often cars are "de-tuned" (ignition timing retarded) when imported from Japan to NZ so that they can run on 91 without pinking. My opinion is you are better off running 96 and getting better performance and mileage (not to mention reduced risk of engine damage). That outweighs the extra 5c/l in my experiences.
BTW the fuel pump problem seems to be a common one.
Your comment about cold nights suggests that it might be worth making some mods to get more cold air to your intake...