i have cng in gli and its zaberdast. gives me 150 km in city and around 175 on outer city...
another pw membr, xain has cng in his altis with lambda controller and its giving around 140km in city (if i remember correctly)..
all the milages given above are for 55 cylinder..
the only problem in cng is backfiring, and its not a problem for toyota, its a problrm for every car and it can be easily dealt with if the setting is good.. btw there is no considerable backfiring in myne gli...
petrol milage of gli was around 10~12.
if the petrol costs you around 1500, then stick to petrol as said by autophile..
sir i havent strangled the throat of my car and it runs great on both fuels.. it all depends on the settings..