Which petrol you are using 91 or 95???
When did you changed plugs??
For injector cleaning Petromin will charge from you 500 riyals or more, and that too is not ultrasonic cleaning, they will put some liquid in your car fuel tank, and after half hour keeping the car at idle they will say ok your injectors are cleaned now. This is what I have seen once.
Its better to go to Toyota company, discuss your problem with them.