Inspector General Michael Horowitz’s widely anticipated testimony next week before the House Oversight Committee has been postponed, as the Justice Department IG has pursued new leads in his review of the Hillary Clinton email investigation, according to a congressional letter and sources familiar with the matter. “It is of the utmost importance that your review be as fulsome, complete and unimpeded as possible,” Rep. Trey Gowdy, R-S.C., the chairman of the committee, wrote in a recent letter to Horowitz obtained by Fox News. Horowitz was scheduled to appear before the committee on May 8. But Gowdy told Horowitz he wants...