Seems like no matter what RPM it's at, the car will stumble/slightly jerk while at cruising throttle, which is basically enough to maintain speed, or lightly accelerate. If I give it some gas or let off the gas the stumble goes away. I only have 1 code and it's for the rear o2 sensor, which does not affect the engine's performance at all. I just seafoamed the engine through a vacuum hose. I'll run another can through the gas tank today. I havent checked the plugs yet, but Id think that would be more of an issue under load, which this is not.