I tried various American Standard Toilets in my powder room. All would clog, thought it was the plumbing, but could not find anything wrong. Even the new, fully glazed, larger trapway A/S would clog. Used to have to plunge about once a month.
Then I found this site:
http://www.terrylove.com/crtoilet.htm
Tried a Toto, and that is all I will buy now. 5 years later, and I have NEVER had to plunger the Toto