Wal-Mart — ah, always Wal-Mart — has plans to open four stores that “will operate at a level that’s 25 percent more efficient than a traditional Wal-Mart supercenter,” according to a representative. The chain, which has a goal of someday having all of its 2,400 U.S. stores reach that level of efficiency, is using tricks it learned from experimental stores in Texas and Colorado. The first of the second-generation stores is set to open its doors on Jan. 23 in Romeoville, Ill.