you are correct.i never gave a final verdict on the case! We would like many people who have driven their new corollas extensively on CNG.their input is of vital imp n could help all current n potential Corolla cng users alot.im a great fan of cng due to it being environmental benefits n it being a local product it helps reducing our import bill. This discussion is to put us all wise n help us making decisions with our hard earn money whether in purchasing a car or paying for cng conversion or cost of fuel! I consider that how wod i have felt if i paid 45k for cng in my new car n then after 50k mileage i wodve to get the valve fixed.if we conclude that cng has no adverse affect on a vvti engine provided xyz are taken care of then it will help many our bros in maintaning their hard earned cars.plz if you can ask any taxi guy who has driven his car on cng for around 100k that wod be gr8 in clearing many doubts and also if more light could be shed on the tech details i.e the setup he uses.this will be of gr8 help.