Any chance you were able to figure out the issue. For the past month I have had something similar. Car acts weird once warm, especially after I shut it down and re-start it warm. The engine will do a few different things at idle/neutral depending on the scenario: Rev up and down between 1500-2200 rpms, stay idling at 1800rpms, or will get stuck around 3000+rpms if I tap the accelerator. I've tried to locate a vacuum leak, but I'm starting to thing its a bad sensor or an electronics issue. I've swapped MAF sensors, TBs, Accelerator assembly, installed new breather lines and T. Checked for vacuum leaks like crazy, reset the TB and reset the CPU. Works fine for the first trip then when I shut it down and restart after a shopping trip the issue resumes. Its drivable, just issues when I'm stopped or in neutral, in gear its ok. No CEL of codes. This is crazy.