The older Toyota fuel injection systems, from here on referred
as Toyota EFI, are analog systems based on Bosch L-jetronic.
Around the mid-80's the Toyota TCCS took over, it is a (8031/8051)
microcontroller based digital system using in-chip ROM.
That means there is no separate ROM chip which could easily be
read and replaced for tuning purposes...
Later versions use more powerful microcontrollers.
The TCCS systems use L-jetronic, MAP, hot-wire and vortex 
type air flow meters depending on application.