check the o2 reading to see if the surge in idle is more fuel or more are (surge cause lean, or rich). Take that info to do an engine load comparison. And that should point you toward something. You seemed to address an air issue, which at idle would stall more likely unless the car started to add fuel to compensate (running lean when not surging). Or if you have too much fuel the car would be cutting fuel to bring the idle back down.. (running rich when not surging). You seemed to address all the air related possibilities exact the two intake sensors, check those. On the gas delivery side, it could be simply the warm up circuit, an injector, even bad o2. But check what your getting with the scan tool.