Hi Texas Honda/2005MDXOwner,
my 04 MDX has a similar issue. The screech appears to come from under the cup holders just behind the transmission. It occurs under braking, whether light or heavy. Do you know if there is a booster fan/blower motor for the a/c under there ? The bushing explanation seems to make sense, but before I go undoing stuff it would be good to know what is under there.