Other Fuel System Tank Assembly problems of the 2004 Kia Motor Amanti

On 6 separate occasions the vehicle has slowed down and "chugged" out of throttle power while initially driving at speeds of anywhere between 35 and 65 mph. If the vehicle does manage to keep driving, it does so in a very jerky way, almost like someone who does not know how to drive stick. I've found that the only way around this jerking is to drive the vehicle in sport-shift mode in a lower gear so that the rpms stay above 3000. Sometimes the vehicle is entirely unresponsive when the gas pedal is pressed, which (multiple times) nearly put me in a severe car accident on busy I-95 in both florida and philadelphia, PA. The check engine light has only ever remained on once, giving an error code p1614: "enhanced traction system engine control module malfunction. " in the past, turning the ignition off and back on immediately has fixed the issue twice. Other times the vehicle needed to remain off for an extended period of time before the problem would clear up. The check engine light came on only 2 of the 6 times the problem has occurred. The first time it came on, it did not remain on although the problem persisted. Currently, the check engine light remains on although the vehicle has been running smoothly since the most recent occurrence of this issue which happened on January 8, 2015. I do believe the problem may be linked to the fuel injectors. I find that adding fuel system cleaner to a full tank of gas every other week helps me avoid having this problem.