At first glance, you'd think Delphi Corp.'s ( DPH ) recent hiring of turnaround specialist Robert S. "Steve" Miller Jr. as its chairman would be good news for General Motors Corp. ( GM ) After all, GM still buys gear worth $15 billion annually from its troubled former parts unit. But in recent years, Miller was quick to restructure distressed parts maker Federal-Mogul Corp. ( FDMLQ ) and Bethlehem Steel Corp. by seeking bankruptcy protection for both. And the last thing GM Chairman and Chief Executive G. Richard Wagoner Jr. needs right now is for his biggest supplier to head into Chapter 11.