Did you get it scanned? If not, better get it done. I think either fuel pump or the injector has some problem.
Top portion of shocks :(....I think you are confusing the complete shock assembly with shocks. Actually the dead shock is brought out of the assembly and then new one is replaced in. I am not sure about Sangin, but if the parts dealer is trustworthy, you can go for it. Kabli are still not advisable.
In winters, due to hard engine cranking in the morning, more battery power is required as well as more fuel. So, it is advisable to avoid engine tune-ups during winters. For a better startup on CNG I have a working formula:
Boil around 1 Litre of water and then pour it on the CNG regulator before starting in the morning. You will get better startup on CNG in winters. (y)