Mitsubishi lancer cng problem

[tabraiz86.ak]

Assalam o allikum
I have mitsubishi lancer 1.3 manual.having a problem on cng.some time car back fire while i use first or 2nd gear.afterwards its work perfect on cng. I have change throttle body
Spark plug, New coils
New plug wir
Air filter..
Someone told me replaced the coil and install baleno coils.
Please suggest..

[addulch]

Try starting your car on petrol and then after the car reaches its operating temperature shift the car to CNG. The issue might be resolved