CNG is itself hazardious for car's health.
anyways CNG satros are running perfectly
but for instance few bad things happened with santro owners.
one of the owner got his gear box broken while driving, he went to claim it even it was under warranty but guys denied they said u shifted gear in speed without applying clutch its all non sense.
as santro is EFi it works good with CNG if installed perfectly.
yet no complaints heard about CNG santro