So finally it's made.
It took me about 3 hours to make it with the help of my mechanic and than an hour in fixing it and adjusting the cable pulling mechanism.
The first picture is when the cable is not pulled, means air as per CNG. The inner plate blocked 60%.

The next two pictures are when the cable is pulled, means on petrol. The inner plate/ butterfly can be seen straight allowing 100 % air to flow freely.

