The resolution was the mechanic put the new pre cat sensor in the post cat location. I had the truck in for some other work and figured I'd have the mechanic slap on the new sensor while he was under there anyway. He just forgot it was pre cat and replaced the wrong sensor. So now I have a pre cat sensor in the post cat location. When I found the mistake I called the mechanic and he had already tossed the other sensor so now I've got a post cat sensor on order. Should have ordered both sensors to begin with.