Cars Q&A

I have Hyundai Santro 2003 Model in which I have retrofitted a CNG KIT. Ever since the kit is installed the sparkplugs are required to be changed very frequently. Every 2000-3000KM I have to change the sparkplug otherwise the car starts giving problems. While changing gear the car stops. Sometimes car vibrates very much. I hardly run car on AC. Please also advise whether I should use AC or not if run on CNG. Thanks and Best Regards Bijay