MANITOWOC, WI (WTAQ)-Manitowoc police are looking for two men they say robbed a south side gas station at gunpoint Sunday night.  Police say at about 8:45 p.m. the men, one armed with a silver handgun, held up Popp's University BP in the 2700 block of S. 10th St.  The suspects forced the clerk into the store's office.  Both suspects were wearing Halloween masks.