Okay thanks. I also think there is some issue with the intake, because even when driving on petrol, it sounds like extra air is going in from somewhere.
I know this because my Santro's air filter housing used to pop open sometimes and then it would stop working on CNG, and when converted to petrol, it would sound like I have a phhata hua silencer when accelerating. The Joy is sounding the same when I push the accelerator.
Any recommendations on who is great at fixing these CNG matters in Lahore?