i am owner of alto vxr 2005 model ... after completing its 195k kms found that engine overhaul is required , was eating too much oil + giving away black smoke ... so i go to the mechanic who did all the work of my car since zero meter (the car was of my father and he has gone to abroad 2 years ago ) took 1 week and the overhaul was done pistons rings clutch plats all things were changed .. totally coasted me around 50k ... after its overhaul i drove it on petrol for its 1k kms running .. was not giving me good pick up even on petrol, i ignored and thought that engine is new and will take some time to get in momentum , after its 1000 kms running changed its oil (Shell 10w40) got tuned and added its CNG belt ... my first experience on cng was terrible ..was taking jerks while gear shifting less of pick up like hell even car's AC is not working just fan is working ... 2 ,3 alag mechanics k pas chakkar lagaey to kehty hain k engine ka kaam theek nahi kiya wapis khulwaou ... dont know what to do ... recently my friend's cultus was overhauled and before completing its running on petrol tried some CNG drive .. it was running like hell ... on CNG in 3rd gear it was doing 100 kph in no time ... can you ppl guide me what to do @xulfiqar bhai please guide