KABUL — With Washington set to send billions of dollars in fresh aid to Afghanistan despite the military drawdown, the U.S. official in charge of auditing assistance programs says “it’s not too late” to address the fraud and mismanagement that has bedeviled the 14-year effort to rebuild the country. In October, SIGAR reported on a compressed natural gas filling station in Afghanistan’s far north that cost $43 million to build but has never been used because there is no demand for the fuel. Since it was created in 2008, SIGAR has identified more than $1 billion in potential savings to U.S.