Thnx 4 ur reply & very informative web site. after reading information from web site, it is now cleared that the cleaning of Injector is not simple as stated by my mechanic, he has checked injectors, 2 injectors r not in working.
Now I decided that first i would like to try cleaning by Liqui Moly (Price Rs700 in karachi), in case of no improvement, then i wll change 2 injectors.
Thnx once again bro