American Standard w/ Sloan Flushmate issue

Have an American Standard 4098 with Sloan power assist that makes a whistling noise after flushing. This whistle lasts for up to 45 seconds. It didn't do this when new and the toiltet is about 9 months old. How do I troubleshoot this issue? Your help is appreciated!

If you go to the Flushmate site, they will have books on it.
You should have the 1-800 number to get a live person to walk you though it too.

http://www.flushmate.com/