When Time Out New York writer Alison Rosen asked former NY mayor Ed Koch if he was gay, he replied with an apparent non sequitur: “When was the last time you performed oral sex on your boyfriend?” The flustered journo said that since she was single now, it had been a long time ago. “I don’t think you should answer that question,” Koch said. “It’s an improper question, and so is yours. My sexual orientation is none of your business, and whether or not you performed oral sex on your boyfriend is none of my business.” But we bet the old grey mayor wouldn’t have minded hearing details about that last time. (Page Six)