I'm not sure about how intelligent the ecu in your tercel is, but there's no way to "tune" the ecu's in most cars.....
the ecu's are usually read only, but you can get a piggy back unit that can be used to tune the car.....but depending on how new your car is, the ecu will usually cause many problems because it is TOO intelligent and can eventually override the tuning
the best results are to get a whole new aftermarket ecu
the ecu's are usually read only, but you can get a piggy back unit that can be used to tune the car.....but depending on how new your car is, the ecu will usually cause many problems because it is TOO intelligent and can eventually override the tuning
the best results are to get a whole new aftermarket ecu