Rather than wasting time and money on silly mechanics and on petrol (7km/lit) what is the problem with you taking your car to the authorized Toyota 3S dealership in your city? Tell them your concerns and they will bring your car back to its design factory specs. No point in wasting money on changing injectors etc. etc. hoping that a "tuka" will work. Today's cars are a bit complex. Regular mechanics armed with a "paichkass and plaas" are not geared up to do a proper job.
After owning over 15 cars over 30 years, I have learnt that there is no substitute for the dealer's workshop from routine service to major jobs. The thing is that your 3S dealer's handles 1000's of cars just like yours on a daily basis plus the shop supervisor has been trained by the Japanese. No mechanic sitting under the tree can compare; no mater how "good" he may be. Your 3S dealer will do a proper diagnostic check, zero in on the problem and fix exactly what needs to be fixed rather than ..... :o
Just my 2 cents worth.