Thanks Xulfiqar for the nice info!!!
The car is with Turbo Engine but turbo was removed during installation of CNG. The CNG gives perfect milage hitting around 200 kms in a 7.5 kgs fill (50 kg cylinder). It accelerates well in third gear, reaches 80+ kms in no time, but in fourth and fifth gear above around 100 ~ 110 km/hr, it starts wheezing. It feels like the engine suddenly lost its breath, the car begines to shutdown; though when the acceleration is reduced , it becomes normal but the wheezing effect lasts for 10-15 more secs too, in after lowering the speed.
My mechanic says, its the turbo air intake set-up that is causing the problem. He is asking me to install that conventional circular Air Intake set-up!!! I am fearing that I might lose the car economy, but yes I love to move beyond 110 by sacrificing it the same time.
What do you say?