All kind of issues on CNG the ones till 2006 have CVT in 1.6L so if it has CNG high chances are that car has already a junkyard transmission.
1.3L came with conventional 4 speed auto which can work on CNG but injector will fail on 40,000 km or around and then you are on junkyard injectors for 1200 per pop since the original ones are 8,400/piece.
One other gift of CNG would be that air intake or box would blow or leak after every 3-6 months causing misfire not to mention you have to block the air on throttle body.
Shift quality of CVT is worse, the 4 speed auto is much better and on par with same model Altis but inferior to Civic.
In 2007 facelift Deewan dropped the 1.6L variant altogether.
The JDM versions are with 1.5L 4G15 CVT engines with much better torque.
The Thai versions does not have any airbag, ABS or navigation etc at all.
So a Lancer with auto transmission is only good if its in petrol.