PF

I have a 1 year old Yorkie, that still, after training, he eats the finest foods, and he won't touch his own poo, but when we go to the park, he is constantly looking around trying to find some, and if he sees it, he eats it. He will pull and tug for me to let him go to some, and the other day i dropped his leash as he leaped out of the car, and he literally darted across a parking lot and took a chunk out of a pile before i could catch him. Don't try to be funny please by saying "just don't take him out" because that would suck. I'm serious, I really need to know what is going on. He also pees in front of my bedroom door if he gets in trouble or if I don't come out, even if I have already taken him for a walk. Do I jut have a really ornery dog? Or could he be mentally challenged?