In my experience, cleaning the throttle body is not required. I have said this on many other treads. It is a gimmick our ustaads have started as a way to make money. In the old days with cars having carby engines, there was the carburettor to clean, points to set, timing to adjust etc. With the EFI car, there is none of that, ergo the "throttle body wash"!! I have owned 5 EFI cars, one of them crossed 350,000km at the time I sold it. Presently the Spectra has 175,000km on it (gives me 10-11km/l in the city with a/c). Not one of these ever had their throttle body washed!
If you are inclined to follow your mechanic's advice about the replacing injectors, I'd suggest having them tested before replacing them outright. You are based in Peshawar, I don't know if there is any place there that has the equipment to test and clean injectors. Logically speaking, with all the EFI cars and diesel ones in Peshawar, there must be one in the city somewhere.
