Hello!
I have and 07 MKX with 139,000 miles and notice similar symptons on the engine vine/hawling while acelerating and moving card along the freeway.
Also, I did a Power Steering Fluid replacement with new Mercon V after the old was was very dark/blackish. However, the problem still there.
Since MKX share same engine as Edge I though I post this for any update on the issue.
My next step was to consider replacing the TSS sensors as explained in below video on Youtube.
sp9239