Salam, I bought Swift DX 2013 in September. I just installed CNG kit last week from a local vendor of LR in Karachi. (I was misguided by someone that Swift does about 18 km in 1 L but the reality is quite different, so installed CNG after 2000 km). You may check there could be a problem with advancer bcoz i had the same engine light problem in the first week of installation then mechanic changed the advancer. now the car is running perfectly on CNG with no light or any problem. You must take your car to some other CNG mechanic of good repute in your city.