i think Lancer 2005 is equipped with an 4G-13 1300 cc multiport efi engine not sure but did you checked the fuel pump & filter. If car was on CNG before at times the fuel pump starts malfunctioning and fail to maintain constant liquid fuel pressure to injectors / injector rail. any drop in fuel pressure to Injectors cause the jerks. thats' my amature opinion,
wait till your thread is read by masters like Xulfiqar, rustam, ser_gtr these guys are regulars and always give correct tips for diagnostics & possible remedies