Slayzen, pretty late reply for your question but here goes. Installing a CNG fuel system without an advancer, emulator and lembda is highly uncalled for. As for your jerking experience on CNG, unfortunately it was not the CNG that was the trouble. I bought one of my friends a Lancer and it had trouble with the CNG in terms of engine stall, RPM drop down at idling and jerking. However, the funny thing is that it was a manual transmission. The actual problem in his case was a leaking air filter that was causing the engine to jerk and die out at idling especially.
The solution was pretty simple in his case - we had the air filter assembly worked out. The air filter assembly was missing a bracket on the upstream of the filter on the lower end. The entire thing was replaced for some 2k and things started working. However, even after that there was some jerking trouble on CNG alone and we discovered that if the air filter were cleaned out every other day or so, there was no trouble. Mind you, the jerking and the loss of power occurred with CNG alone but not with gasoline given of course the higher calorific value and the ability to tolerate greater disturbances in the overall air fuel mixture.
[TABLE="class: outer_border, width: 700, align: center"]
<tbody>[TR]
[TD]Substance[/TD]
[TD="align: center"]LFL/LEL in %[/TD]
[TD="align: center"]UFL/UEL in %[/TD]
[TD="align: center"]Autoignition temperature[/TD]
[/TR]
[TR]
[TD][/TD]
[TD="align: center"]by volume of air[/TD]
[TD="align: center"]by volume of air[/TD]
[TD="align: right"][/TD]
[/TR]
[TR]
[TD]Gasoline (100 octane)[/TD]
[TD="align: center"]1.4[/TD]
[TD="align: center"]7.6[/TD]
[TD="align: right"]246?280 ?C[/TD]
[/TR]
[TR]
[TD]Methane (natural gas)[/TD]
[TD="align: center"]4.4?5[/TD]
[TD="align: center"]15?17[/TD]
[TD="align: right"]580 ?C[/TD]
[/TR]
</tbody>[/TABLE]
If you look at the table above, you will notice the LEL (lower explosive limit) which represents the lowest limit at which the fuel will ignite in air. If you end up disturbing your air fuel mixture by any means, such as a leaking air filter or a dirty air filter, you will end up with what local mechanics call "engine over ho gaya hai". Gasoline can work with high doses of leaking air but methane (the largest component of CNG) cannot do so. Similarly, gasoline can work with low doses of air, such as when your air filter is clogged up but again methane fails to fit the bill. The fuel system in any car is designed to keep the air fuel mixture optimised within the LEL and the UEL limits but any disturbance will cause problems such as your engine jerking, dropping down engine speed and eventually shutting down. Also, please notice the auto-ignition temperature that can be taken as an indicator of how easily a fuel will burn. The higher the auto-ignition temperature, the harder to burn the fuel in question. This is another reason why CNG is more difficult to deal with in terms of installation and troubleshooting.
Another strange thing, the filters for Lancers are typically being imported. Other than a Lancer, I have not seen the need to constantly clean out the air filter with any other JDM vehicles. The air filter for Lancers are also markedly different in terms of the internal construction and flow patterns and I suspect that the filter film being used might be too tightly knit too causing this problem.