Here is the the update- Gave my Ford Corsair to another mechanic who has got computer diagnostic systems to see what is going wrong with the fuel system.
The diagnostic system interestingly told that my car was actually running lean(15.0:0)/ not rich and still blowing some smoke under acceleration. This time the mechanic told me that he reckoned that the smoke was blue/not black. The other two mechanic who had a look at it told me that it was black and one mechanic showed me it was more black than blue when he pressed the acceleration really hard.
The current mechanic didnt do anything more, but he charged 170 bucks for diagnosis thing. He told me to use injector cleaner and see how it goes!
Really pissed of these repair things and have decided to drive as it is until it blows and dies!