Re: I bought a stinky diaper!
First, I wouldn't believe that "use a mainstream detergent instead of Country Save" thing. Country Save has the same types of ingredients as mainstream detergents, without the stuff that sticks to the diaper making any sort of buildup worse. For enzymes (which I'm pretty sure don't help with set-in ammonia) you can add a bit of bac-out or Nature's Miracle. I have often tried that "just use Tide a few times and it'll strip" thing a few times and it just never works.
What does, is a washing soda soak. 2 Tablespoons of washing soda in a gallon of warm water, soak overnight.