Hi there,
I have kind of same issue with my cultus efi. The pick is very bad on cng and if I turn on the ac it starts vibrating and engine stops. After I start it on cng, it starts and stops. If I start on petrol, it works fine and I can switch back to cng after an hour or so. Another issue: if I fill cng and start the car, engine stops on cng, i need to run on petrol and then switch to cng. Got tuned recently. Plugs serviced, filter changed, throttle body servicd, oil and oil filter changed. What could be the issue? Current?