You can get rid of the air pump, and block off some of the emissions lines, there is pleantly of performance parts for 3tc's in the states (3tc performance brd racing)
Carb tuning: The way I did mine was I replaced all the plugs, leads, reset dizzy points, reset timing first, then I played with the carb. The way I did was turn in the idle mixture screw till it runs rough then very slowly turn it out till it sounds smooth, then turn it out another 1/4-1/2 a turn. Thats how I did mine and now I'm getting about 10L/100kms, which I think is pretty good.
If you live local I could give you a hand, where in QLD are you?
Also got a picture of your car?