How do we come to know about the air fuel ratio at each RPM and Throttle position.

use a wideband o2 sensor (cost -10000 rs)which comes with a cd , hook it up to your computer via a conditioning circuit( very reliable) or go to your local jap car tuners and ask them they will get you an a/f meter guage (dnt know how they hook it up exactly but should be the same and dnt know how reliable they are )

I really don't know about the availability in India, but innovate motorsports has a low-dollar logger. You might be able to get a used one?

www.innovatemotorsports.com