Two NYPD cops are being eyed in the Long Island serial slayings after investigators learned they got into trouble for hiring prostitutes while working for the department, according to sources familiar with the probe. One cop was forced out of the job in the 1990s when his supervisors learned he spent time pursuing hookers and paying street walkers and down-and-out women for sex while he was supposed to be on patrol. An internal investigation led to his resigning under pressure, one source said. The other officer still works for the NYPD but was stripped of his gun and badge years...