By Tomi Kilgore Stock falls more than 20% from December high after Wells Fargo analyst cuts rating, price target to the lowest on the Street Shares of Boeing Co. kept falling Tuesday, enough to enter “bear-market” territory, after a downgrade by Wells Fargo, which said there’s a good chance the Federal Aviation Administration’s investigation won’t be “clean.” The FAA’s probe “increases significantly” the risk that production and deliveries will be curtailed, analyst Matthew Akers wrote, in a note titled, “FAA audit opens up a whole new can of worms.” He doesn’t see enough upside for Boeing’s stock to justify that risk. The aerospace and defense giant’s stock (BA) sank 7.1% in morning trading toward a two-month low. The $15.36 price decline was shaving about 101 points off the price of the Dow Jones Industrial Average DJIA, which fell 126 points, or 0.3%. (Read more about how Boeing’s stock can affect