@fyq
I remember a mechanic telling me that in cultus VXRi this system is already provided.So no matter from where u get the cng filled,car performs the same.
As for the DIY. It's a gud DIY for those who wants/have air blockage in inlet.I however, have tunned my car without any air-blockage.
The thing i'm interested in or should I say make a real difference is to completely remove the CNG venturi while driving on petrol.Coz for driving on petrol,venturi restricts more then 60% of airflow by it's design.