We have an ST743SD which I installed about two years ago. The other end of the house has a Kohler Wellworth(?) toilet that is original to the 1958 house. The Toto retains marks in the bowl about 90% of the time after a bowel movement, while the original toilet almost never does. I have tried flushing before using as well as flushing during use to try to alleviate the problem but to no avail. This is not a chronic problem when using toilets elsewhere. I am wondering if there is perhaps a problem with our toilet, as other reviews don't seem to indicate this being a problem with this model? I have been happy with every other aspect of the toilet, and it ALWAYS removes all the contents of the bowl, even if it leaves a reminder that they were there.