Ouch
I( get an average 30mpg, but I rarely do any town driving, its mostly hour long runs to a mainline train station, or longer runs if I drive to wherever I happen to be working.
I have changed most of the components of the FI system, including the injectors.
How old is the car, and do you have KE-JET FI?
If so is the lambda working properly?
Has it been set up correctly before having the co2 set, presumably by reading from the exhaust?
There is a means to set up the engine by measuring voltages, before tuning by setting via the co2
You've changed the autobox oil and filter, all you can check now is that the vacuum leads to the box are present and sealing well, after that I think there are adjustments you can make, but you need someone wiser than me to advise on that.
Tony