sorry to say there nothing true in ur post,u can hardly find any honda city on petrol.only ppl who r keeping it as a 3rd car do it.rest all of the city owners hav got cng in it.
regarding the problem,i also hav the same setup.city idsi manual wid cng.hav driven 11,000kms on cng.i got it tuned 3rd day after getting in cng,till the day its running fine.not a single jerk given since the day.
its giving 110km on a cylinder wid full time 100% ac on in city.
the drive is smooth.i got advance nd emulator no lambda.its working perfectly.
no 1 percent change in engine sound.if u get it done frm a good mechanic.
in short,therez nothing as problems on city cng as ppl hav been saying....just go fo rit...(Y)