Let's check for codes again to start with. Then there are a couple major things that cause a high idle and you are touching on them. However, we can't eliminate them based on what you did. We need to actually test them, preferably with a scan tool.
The MAF is the most common cause. Here is a video of one on a similar MAF:
It could also be an EGR valve hanging open and the other major cause are vacuum leaks. Seeing as how you tested for vacuum leaks we can bypass that for now.
I would suggest starting with checking for codes and seeing if any point us in the correct direction. If not, test the MAF and then we can move onto testing the EGR.
Images (Click to enlarge)
Friday, February 14th, 2020 AT 5:50 PM