Well this is embarrassing. But not as embarrassing as it would be if I was a designer at American Standard.
I've been dealing with a clogging AS toilet for over a year. I couldn't figure out why it was happening, and I guess they don't know either. I called their customer service line last week, and was told by the girl on the other end, that I had bought one of two models that had a history of clogging, it was out of warranty, and to go buy another toilet. Thank you............Goodbye.
Earlier, I had cut out my plumbing in the basement, checked venting, and reinstalled new. I couldn't imagine that a company would sell a product that didn't work...........I must have done something wrong. No help with the new plumbing.
Today I decided to really study the problem, in hopes that I could re-engineer the toilet to work right. I have a Kohler toilet upstairs that has never had a problem. The tank to toilet holes are the same size, both are 1.6 GPF, and both have almost identical floats and flapper valves.
What's different? After a couple of trips back and fourth, I found only one thing..............the tank on the Kohler was smaller.
Hmmm. Well the only logical explanation, (to me), is that the smaller tank resulted in an increased velocity of the water from the tank to the toilet, during the flush.
I tested my theory, and my downstairs toilet now flushes perfectly.
This fixed it. A two liter bottle, filled with water.
Hopefully someone else can use this information. I'm feeling kind of dumb at the moment.

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