I just give a brief history before giving the updates...
Everything was fine with my Cuore, on its 20,000 kms I wanted to have its routine checkup, went to Toyota workshop, they did engine tune up and brake service.
After this tuning CNG consumption of my Cuore degraded much, went back to them but they didn't attended me well, just adjusted the idle race and showed me the gate. After this craftsmanship, the rpm at idle state decreased too much. Out of helplessness I went to local CNG mechanic to have my problem solved, he did CNG adjustment but after that consumption was better but the pick was down like hell.
Now here is the update....after going through all this mental disturbance, I wrote a letter to Toyota customer services, the next day I received a call to give them a visit.
On this monday I went there with my car, the mechanic first did road test and said that everything is fine (as normally all mechanics do) but as there was pressure from Customer services he had to satisfy me. So he had to do some work, he checked the setting of starting point, then he cleaned the air intake pipe and closed the half of it with tape, then he adjusted the gas settings.
After this I find my car in good pick and consumption is yet to be tested.