I am afraid to drive the car off the property. I just drive around here and it does good and gradually moves to 82C in ~20 min.

Then goes to 85C and hangs or moves slowly to 95 and then on to 100C and starts missing. (actually starts missing at 90C; just gets progressively worse).

Leads me to believe maybe more than one problem; but, I tend to inculde the cat convt.