In some cases of CNG installation there had been reports of ECU burning due to faulty electrical wiring. I have also heard of air intake manifold blowing away due to back firing and some other similar incidents. I am not sure that how true these stories are. But still on the safe side it is better to get it installed from Honda service station as you will retain your car's warranty.
Another question is that is it possible to install CNG in VTEC 1.5 ltr model. Could you please confirm it and put it on this forum or mail me to firstname.lastname@example.org. Actually I want to buy this car in Pakistan but presently I am not in Pakistan. I will appreciate your help if you could confirm it from Honda service station. Thanks.