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I think Mike and AFJuvat gave good explanation here. I still think the O2 closed loop operation in conjunction with the ECM idle closed loop control fight against each other causing the idle to move up. The easiest way to confirm this in your case Scott is to just disconnect the O2 sensor when you observing the engine running at 1100rpm. If the engine speed drops to normal levels then you know the problem is related to what I said. In this case I think you have 3 option:
1. Bad O2 sensor.
2. Temperature sensor is giving wrong readings.
3 Mixture screw is set incorrectly at the air flow meter.
A good O2 sensor will try to compensate for case 2/3 above thus causing the idle to move up. In either case I suspect the mixture to be actualy right, just little bit more idle.
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