EFI tuning is a science that is carried out at the factory using megabuck computers and teams of engineers. What results is usually a specific "fuel map" for each car using a particular engine/ trans combo. In older cars this specified program was replaceable as a chip known as an electronically erasable programmable read only memory or EEPROM for short. Performance gains could be made by substiuting the chip with a performance type. Usually these chips would have longer injection times and allow better fuel delivery under acceleration, on some cars you could fool the computer by putting a resistor in the water temp sender making it think the engine was colder than it really was and so adding more fuel; unfortunately both these methods were not much good without extra modifications like bigger air inlets for instance. A stand alone computer can be programmed from a laptop to alter the fuel map for ultimate performance gain but it is expensive and needs to be primarily set up by computer boffins to get the car running in the first place, then you go for a blast and adjust the fine tuning. Transmission shift points are often set as part of the powertrain control module which is a fancy name for engine and trans computer in one. The same can be done to them as the transmissions controlled by them are shifted using electric solenoids inside the transmission, you can also make a shift alteration device by tapping into the wiring and making a manual control system, but I would do a fair bit of research before I started because you can trash a transmission very easily by putting it in two gears at the same time, make sure the solenoid sequence is right! So if you decide to do this sort of stuff you might even be able to make a career of it by selling your devices to others, good luck !!!
Cheers from Australia