timing adjustment obsessed Options

[eldrewado]

hey everyone. ive got a 99 5sfe celica. as many of you know this means i have a non adjustable distributer. ive been told the computer adjusts the timing.
so my questions are: how does the computer adjust the timing? what sensors does it use to read the timing? does anyone know how the sensor or ecu does what it does in the area of timing? my goal is to "trick" the computer into advancing my timing a bit for better highway mileage and maybe some more power. surely there has to be a way to do it. ive heard i could do it with the timing belt, but then i heard i couldnt. any input greatly appreciated. thanks

[eldrewado]

actually i read that if you try to put too much resistance on one sensor the ecu will get mad but i figure just a little split up between 3 will go unnoticed. im trying to go for gas milage. ill try one thing at a time and see what happens. a have the torque app for my phone so i can see engine data in real time. if anything goes wrong ill know i just wanted to see if anyone knows something i dont. like how the timing is actually adjusted. is it an electromechanical linkage?