The code you mentioned would seen to suggest a fuel trim fault. This is backed up somewhat by the way you describe the O2 sensor figures. Have you looked at MAF and 4 gas figures?
Can you comm with the valvetronis module? Any codes?
If it is a trim code that is setting the MIL and it takes a while to reset, also it is more evident at idle from what you said, that makes it sound like a vac leak.
Did this car have a service in the recent past by any chance? Maybe an oil top up?