FORMER HIGHFLYER Plains Exploration & Production (ticker: PXP) is one stock that has run out of gas as energy prices pulled back. However, the oil and natural-gas exploration company has a new investor in billionaire George Soros who has scooped up nearly 6.5 million of the downtrodden shares in 2009. On May 4 Soros's fund, Soros Fund Management, disclosed it now owns 6,467,400 million shares, or a 5.4% stake in the Houston-based Plains Exploration. Soros' hedge fund did not show any stock holdings as of Dec. 31, 2008, meaning the shares were purchased at some point in the last four...