My first time on Pakwheels. I have a '98 Margalla had the engine overhauled from Sultanabad in Karachi. Now I'm driving it in Islamabad. Issue; I had a major fuel consumption issue, so I took it to an ustaad in Pindi. He suggested to change jets on the carburetor. Ok, the fuel consumption issue was resolved but three new problems arose. The acceleration seems strangulated (not quick enough as before), secondly is a very jerky and smoky cold start, the smoke and jerks vanish when the car warms up. Lastly, smoke being emitted when it's warm and above 100 Km/h. I am told that this smoke is the carbon accumulated over years of running on CNG (2004-2016). So, this carbon has to be forced out and that's why the smoke comes. Well, many questions, I await a reply.