[Rick Parker]

All currrent OEM cars utilize some sort of fuel injection since it is controlled by a group of sensors and a computor. It generally does a good job and emissions (the original reason for EFI) are kept low and drivability is very good. It sounds like the computor is losing it settings or a sensor is going bad and sending varying information that the computor is making adjustments for and ultimately affecting the drivability as you have stated. Start with the sensors, check the values when cold and hot, then move to the ECU.