I have problems with a new (installed about 1 yr. ago)Kohler K-3420-EB/K-3421-PB toilet. When it is flushed (even with water ONLY)it almost overflows the bowl every time. It comes all the way up to the top. I have plunged it, snaked it with a 1/4 snake, called Kohler, and had a plumber in to check the sewer & snake it. The other two older, non water saving, and non Kohler toilets in the house work fine. This commode is unusable!!! My last resort is to JUNk the toilet and take a loss, and find a used, non water saving toilet!!! Can You HELP!!!!!