water backs up in bowl, there are no clogs in the privously routed out in drain line.

Well, either there's something blocking the toilet's built-in drain path or you have a cast iron pipe that has rusted itself mostly shut, but still large enough to let the Drain Auger right through (this is the most common cause of your problem).

- Remove the toilet and floss the toilet drain path with a Snake or Drain Auger. The cast iron pipe would need to be chiseled back to its full diameter with a screwdriver and maybe a gentle hammering. But, you'll need to vacuum-out ALL of the chiseling debris before re-installing the toilet, you don't want loose rust rusting out the rest of your plumbing.