GM Leads Stronger U.S. Vehicle Sales  DETROIT (Reuters) - General Motors Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=GM.N target=/stocks/quickinfo/fullquote"&gt;GM.N&lt;/A&gt; on Friday  said its U.S. sales soared 20.5 percent in September as  month-end incentives from the world's largest automaker lured  consumers back to dealerships after three months of weaker  results.