Despite this thread having drifted off topic, I wanted to just update it.
People were right, hall sensor. I was mixed up when I wrote that the car ran without it plugged in. In my defense, it was christmas day and I was, obviously, distracted between when I had the problem and wrote the post.
The problem with idle was caused by a vacuum leak from the vacuum hose to the HCV having pulled out. If you strip off the outer flexible housing of the connector you can see numbers (on what remained of the hard plastic) that show the polarization to plug it back in. So, a new connector ordered, the old one wrapped with self-sealing tape, the HCV plugged in, everything is good (except the weather).
I need to look into that heat shield, it definitely seems like a good idea.
thanks to all,