Sallam , I have a problem with my car.......there is a clear air sucking sound coming from the air filter box at the initial throttle... another issue I am facing is when the car is cold and change over to cng the rpm goes too low and engine stopped sometimes if I remove my foot from the paddle.. and also the car runs like any old underpowered car. the car is giving very less fuel average on cng as well . on petrol I didn't check the average. I tuned up my cng kit but still not giving more the 60 km in 8kg before it was giving me 100 sometimes more than that. the car is also knocking while shifting gears on both cng and petrol. I m too much worried about it. I already changed new spark plugs oil, oil filter and air filter... the throttle body also cleaned with carb cleaner.. but the problem still persist... suggestions would be highly appreciated in this regards.... thanks