I do not think that your warranty is finished, because I bought City 2005, and just after 300KM I put CNG in that. After some days, car was hit by road ramp from below and power steering was not working properly. Honda City sales not only fixed that problem, but also re-adjusted the CNG pipes and said to me that this is company policy on the whole but they do not bother a lot any more. This is another story that in last three years I have ever noticed CNG related problem in my car, best performance though I have driven 48K.