We tried it on CNG, lakin it was soooo weak and slow that we disconnected it. Never got the chance to check the milage.. Lakin I guess koi acha CNG Tunner fix kar lay is problem ko.
Yes ji, The pipe fits on the stock carby, NOTHING changed/done on the engine, it just sits on it and two bolts hold it down on the stock carby fittings, no extra bolts/touching made on the carby or the engine.
In short: Kuch bhi nahi karna parta carby k ander ya bahir, bas purana stock intak eutaro aur yeh luga do, simply takes 5 mins to do everything 
Come and get it whever you want, kyun k it is hand made, tailored-made for everycar, depends where we find space to squeeze in the intake filter of your choice, takes 1 hour to make and we'd design it in whatever form you want. Agar bonet sey bahir nikalna hai to woh bhi ho jaye ga, hehehe
Just kidding 
Cheers bro 