NEXTEL CUP: THE RACE BEFORE THE CHASE: Mayfield comes up with &lt;b&gt;...&lt;/b&gt; Richmond --- With the stakes as high as they #39;ve ever been in a  quot;regular-season quot; Nextel Cup race, Jeremy Mayfield turned in the performance of his career, winning the Chevy Rock and Roll 400 at Richmond International Raceway and clinching a berth in the 10 